#include <iostream>
using namespace std;

int main()
{
int n, m, i, x;
int f[10010] = {0};
int w[10010] = {0}, u[10010] = {0};
cin >> n >> m;
for (i = 0; i < m; ++i)
cin >> w[i] >> u[i];
f[0] = 0;
for (i = 0; i < m; ++i)
for (x = w[i]; x <= n; ++x)
if (f[x - w[i]] + u[i] > f[x])
f[x] = f[x - w[i]] + u[i];
cout << f[n] << endl;
return 0;
}