#include <bits/stdc++.h>
using namespace std;
int n,M,a[1001],v[1001],f[1001][1001];
int main(){
cin>>M>>n;
for(int i = 1;i <= n;i++){
cin>>a[i]>>v[i];
}
for(int i = 1;i <= n;i++){
for(int j = M;j >= 1;j--){
if(j >= a[i]){
f[i][j] = max(f[i - 1][j],f[i - 1][j - a[i]] + v[i]);
}else{
f[i][j] = f[i - 1][j];
}
}
}
cout<<f[n][M]<<endl;
return 0;
}
/*
70 3
71 100
69 1
1 2
*/