代码自认为十分好懂

#include<cstdio>
using namespace std;
#define ll long long
ll cal(ll a, ll b, ll p)
{
    ll ans = 1 % p;
    for (; b; b >>= 1)//个人码风原因，也可使用while循环额外加b >>= 1
    {
        if (b & 1)
            ans = ans * a % p;//及时取模防止爆掉
        a = a * a % p;//及时取模防止爆掉
    }
    return ans;
}
int main()
{
	ll a, b, p;
	scanf("%lld %lld %lld", &a, &b, &p);
	printf("%lld", cal(a, b, p));
    return 0;
}