# include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
long long a[N];
string s, s1;
long long q, n, k;
int main() {
    scanf("%lld", &q);
	while (q--) {
        scanf("%lld%lld", &n, &k);
		cin >> s;
		long long cnt = 0;
		for (long long i = 0; i < n; i++) {
			if (s[i] == '0') {
                a[cnt++] = i;
            }
		}
		for (long long i = 0; i < cnt; i++) {
			if (k >= a[i] - i) {
                k -= (a[i] - i);
                a[i] = i;
            } else {
				a[i] -= k;
				k = 0;
			}
		}
		s1 = s;
		for (long long i = 0; i < n; i++) {
			s1[i] = '1';
		}
		for (long long i = 0; i < cnt; i++) {
			s1[a[i]] = '0';
		}
		cout << s1 << endl;
		s = "";
		s1 = "";
	}
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
int a, b, c, d;
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		int flag = 1;
		cin >> a >> b >> c >> d;
		for (int j = b; j >= a; j--) {
			for (int k = c; k >= b; k--) {
				for (int l = c; l <= d; l++) {
					if ((j + k) > l && (j + l) > k && (k + l) > j) {
						printf("%d %d %d\n", j, k, l);
						flag = 0;
						break; 
					}
				}
				if (flag == 0) {
					break;
				}	
			}
			if (flag == 0) {
				break;
			}
		}
	}
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
int main() {
	int t;
	scanf("%d", &t);
	while (t--) {
		int n, m;
		scanf("%d %d", &n, &m);
		if (n == 1 or m == 1) {
			printf("1 1\n");
		} else if (n <= 3 and m <= 3) {
			printf("2 2\n");
		} else {
			printf("%d %d\n", n, m);
		}
	}
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
string s = "codeforces";
char c, c1;
int t;
int main() {
    cin >> t;
    int len = s.size();
    for (int i = 0; i < t; i++) {
        cin >> c;
        bool flag = 1;
        for (int j = 0; j < len; j++) {
            if (c == s[j]) {
                flag = 0;
                printf("YES\n");
                break;
            }
        }
        if (flag) {
            printf("NO\n");
        }
    }
    return 0;
}

# include <bits/stdc++.h>
using namespace std;
long long t, n, cnt, hi;
int main() {
    cin >> t;
    while (t--) {
        cin >> n;
        cnt = 0;
        for (int i = 0; i < n; i++) {
            cin >> hi;
            if (hi == 1) {
                cnt += 1;
            }
        }
        cout << n - cnt / 2 << endl;
    }
    return 0;
}

# include <bits/stdc++.h>
using namespace std;
long long a, b, n, m, sum1, sum2, ans;
int main() {
    int t;
    cin >> t;
    while (t--) {
        cin >> a >> b >> n >> m;
        sum1 = n / (m + 1);
        sum2 = n % (m + 1);
        ans = sum1 * min(a * m, b * (m + 1)) + sum2 * min(a, b);
        printf("%lld\n", ans);
    }
    return 0;
}

# include <bits/stdc++.h>
using namespace std;
int main () {
	long long n, m, a;
	cin >> n >> m >> a;
	cout << (long long) (ceil (1.0 * n / a) * ceil (1.0 * m / a));
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
int n, k[1001], N = -100000000000;
string name[1001];
map <string, int> m;
map <string, int> a;
int main() {
    cin >> n;
    for (int i = 0; i < n; i++) {
    	cin >> name[i] >> k[i];
    	m[name[i]] += k[i];
    	a[name[i]] += k[i]; 
	}
	for (int i = 0; i < n; i++) {
		N = max(N, m[name[i]]);
	    m[name[i]] = 0;
	}
	for (int i = 0; i < n; i++) {
		m[name[i]] += k[i];
		if (m[name[i]] >= N && a[name[i]] == N) {
			cout << name[i];
			return 0;
		}
	}
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
string s1, s2;
int main() {
	cin >> s1 >> s2;
	int xa = s1[0] - 'a' + 1;
	int ya = s1[1] - '0';
	int xb = s2[0] - 'a' + 1;
	int yb = s2[1] - '0';
	int n = max(abs(xa - xb), abs(ya - yb));
	printf("%d\n", n);
	while (n--) {
		if (xa > xb && ya > yb) {
			xa--;
			ya--;
			printf("LD\n");
			continue;
		}
		if (xa > xb && ya == yb) {
			xa--;
			printf("L\n");
			continue;
		}
		if (xa > xb && ya < yb) {
			xa--;
			ya++;
			printf("LU\n");
			continue;
		}
		if (xa == xb && ya > yb) {
			ya--;
			printf("D\n");
			continue;
		}
		if (xa == xb && ya < yb) {
			ya++;
			printf("U\n");
			continue;
		}
		if (xa < xb && ya > yb) {
			xa++;
			ya--;
			printf("RD\n");
			continue;
		}
		if (xa < xb && ya == yb) {
			xa++;
			printf("R\n");
			continue;
		}
		if (xa < xb && ya < yb) {
			xa++;
			ya++;
			printf("RU\n");
			continue;
		}
	}
}

# include <bits/stdc++.h>
using namespace std;
int main() {
	int n;
	scanf("%d", &n);
	if (n == 2) {
		printf("NO");
	} else if (n % 2 == 0) {
		printf("YES");
	} else {
		printf("NO");
	}
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
int main() {
	string s;
	int cnt = 0;
	cin >> s;
	for (int i = 0; i <= s.size(); i++) {
		if (s[i] == '4' || s[i] == '7') {
			cnt++;
		}
	}
	if (cnt == 4 || cnt == 7) {
		printf("YES");
	} else {
		printf("NO");
    }
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
string s;
const int N = 5010;
int a[N], b[N]; 
int main() {
	cin >> s;
	int len = s.size();
	if (s[0] == 'a') {
		a[0]++;
	} else {
		b[0]++;
	}
	for (int i = 1; i < len; i++) {
		a[i] = a[i - 1];
		b[i] = b[i - 1];
		if (s[i] == 'a') {
			a[i]++;
		} else {
			b[i]++;
		}
	}
	if (len == 1) {
		printf("1");
		return 0;
	}
	int mx = 0;
	for (int i = 0; i < len; i++) {
		for (int j = i + 1; j < len; j++) {
			if (i - 1 < 0) {
				int cnt = a[i] + b[j] + (a[len - 1] - a[j - 1]);
				mx = max(mx, cnt);
			} else {
				int cnt = a[i] + (b[j] - b[i - 1]) + (a[len - 1] - a[j - 1]);
				mx = max(mx, cnt);
			}
		}
	}
	printf("%d", mx);
	return 0;
}

# include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 10;
int a[N];
int main() {
	int n, k;
	scanf("%d%d", &n, &k);
	for (int i = 0; i < n; i++) {
		scanf("%d", &a[i]);
	}
	sort(a, a + n);
	if (!k) {
		if (a[0] > 1) {
			printf("1");
			return 0;
		} else {
			printf("-1");
			return 0;
		}
	}
	if (a[k] == a[k - 1]) {
		printf("-1");
		return 0;
	}
	printf("%d", a[k - 1]);
	return 0;
}