#include <iostream>
#include <vector>
using namespace std;
int a[10010],b[10010];
int main(){
    int n,t;
    cin>>t>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i]>>b[i];
    }
    vector<vector<long long>> dp(n+10,vector<long long>(t+10,0));
    for(int i=1;i<=n;i++){
        dp[i][0] = 0;
        for(int j=1;j<=t;j++){
            if(a[i]>j){
                dp[i][j] = dp[i-1][j];
            }else{
                dp[i][j] = max(dp[i-1][j],dp[i][j-a[i]]+b[i]);
            }
        }
    }
    cout<<dp[n][t];
    return 0;
}