#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstring>

using namespace std;

long long a[][],f[],n,m,a1[],b1[];

int main()

{

    cin>>n>>m;

    int i,j,k;

    for (i=;i<=m;i++)

      cin>>a1[i]>>b1[i];

    for (i=;i<=m;i++)

      for (j=;j<=n;j++)

        a[i][j]=a1[i]*pow(j,b1[i]);

    memset(f,,sizeof(f));

    f[]=;

    for (i=;i<=m;i++)

      for (j=n;j>=;j--)

        for (k=;k<=n;k++)

          f[j]=min(f[j],f[j-k]+a[i][k]);

    cout<<f[n];

}