#include<iostream>
using namespace std;
int main(){
	int T,m,a[105][1005],t[105],v[105];
	cin>>T>>m;
	for(int i = 1;i <= m;i++) cin>>t[i]>>v[i];
	for(int i = 1;i <= T;i++){//shijian
		for(int j = 1;j <= m; j++){//dijizhongyao
			if(i-t[j] < 0) a[i][j] = a[i][j-1];
			else a[i][j] = max((a[i-t[j]][j-1] + v[j]),a[i][j-1]);
		}
	}
	cout<<a[T][m];
	return 0;
}