#include<bits/stdc++.h>
int main(){
	for(long long i = 1, tot = tot * scanf("%lld", &tot), n = n * scanf("%lld", &n), val[105], sum[105], f[1005] = {0};i <= (n << 1) + 1;i++) if(i <= n) scanf("%lld%lld", val + i, sum + i); else for(int j = tot;j >= 0 ;j--) if(i == (n << 1) + 1) return 0 * printf("%lld", f[tot]);else if(j >= val[i - n]) f[j] = std :: max(f[j - val[i - n]] + sum[i - n], f[j]);
}