#include<bits/stdc++.h>
using namespace std;
struct dana{
     int qs;
     int kc;
     int sl;
}a[105];
bool cmp(dana x,dana y)
{
     return x.qs < y.qs;
}
int main ()
{
     int m,n;
     cin >> m >> n;
     for (int i = 0;i < n;i++)
     {
          cin >> a[i].qs >> a[i].kc;
     }
     sort (a, a + n,cmp);
     int sum = 0;
     int cnt = 0;
     for (int i = 0;i <n;i++)
     {
          for (int j = 0;j < a[i].kc;j++)
          {
               
          if ((sum + a[i].qs) <= m )
          {
               cnt ++ ;
               sum += a[i].qs;
          }
          }
     }
     cout << cnt;
     return 0;
}