#include<iostream>
#include<algorithm>
using namespace std;
long long w[1000001],v[100001],f[10000001][100000001];
int n,m;
int main(){
    cin>>m>>n;
    for(long long i=1;i<=n;i++){
        cin>>w[i]>>v[i];
        w[i]*=v[i];
    }
    for(long long i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
        f[i][j]=max(f[i-1][j],f[i-1][j-w[i]]+v[i]);
        }
    }
    cout<<f[n][m];
    return 0;
}