dp question

#include "bits/stdc++.h"
using namespace std;

int helper(int idx, int s, int n, vector<pair<int,int>> &diff, vector<vector<int>> &dp){
    if(idx >= n)return 0;
    if(dp[idx][s] != -1)return dp[idx][s];
    int ans1 = (diff[idx].first <= s ? diff[idx].second + helper(idx + 1, s - diff[idx].first, n, diff, dp) : 0);
    int ans2 = helper(idx + 1, s, n, diff, dp);
    return dp[idx][s] = max(ans1,ans2);
}
int main(){
    //Write here code...
    int s; cin >> s;
    int n = 5;
    vector<int> curr(n), future(n);
    for(auto &x : curr)cin >> x;
    for(auto &x : future)cin >> x;
    vector<pair<int,int>> diff(n);
    vector<vector<int>> dp(n, vector<int>(s + 10,-1));
    for(int i = 0; i < n; i++)diff[i] = {curr[i], future[i] - curr[i]};
    sort(diff.begin(),diff.end(),[](pair<int,int> &a, pair<int,int> &b){
        if(a.second == b.second)return a.first < b.first;
        return a.second > b.second;
    });
    cout << helper(0, s, n, diff, dp);
}