include <bits/stdc++.h>
using namespace std; int t[101], w[101], f[101][1001];
int main() {
int T, M;
cin >> T >> M;
for (int i = 1; i <= M; i++){
scanf("%d%d",&t[i],&w[i]);
}
for (int i = 1; i<=M; i++){
for (int j = 0; j<=T; j++) {
f[i][j] = f[i-1][j];
if (j-t[i]>=0){
f[i][j] = max(f[i][j], f[i-1][j-t[i]]+w[i]);
}
}
}
cout << f[M][T] << endl;
return 0;
}
