rqnoj 117

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
int main()
{
    int n,m,a,b;
    scanf("%d%d",&n,&m);
    long long now,w[m+1][n+1],f[m+1][n+1];
    memset(w,0,sizeof(w));
    memset(f,0,sizeof(f));
    for(int i=1;i<=m;i++){
        scanf("%d%d",&a,&b);
        for(int j=1;j<=n;j++){
            now=j;
            for(int k=2;k<=b;k++) now*=j;
            now*=a;
            w[i][j]=now;
            if(i==1) f[i][j]=w[i][j];
            else f[i][j]=499999999;
        }
    }
    for(int i=2;i<=m;i++)
      for(int j=1;j<=n;j++)
        for(int k=0;k<=j;k++)
          if(f[i][j]>f[i-1][k]+w[i][j-k])
            f[i][j]=f[i-1][k]+w[i][j-k];
    printf("%lld\n",f[m][n]);
    return 0;
}