What you have to do in this problem is:

• receive the input from the Standard Input;
• find \(A+B\);
• find the index of the correct choice; and
• print the answer to the Standard Output.

If you have trouble in the first and fourth, you can learn in the following way:

• read the document of or article on your programming language;
• view other contestant’s code in “all submissions” to learn how to input and output.

The second can be achieved by adding variables.
The third can be achieved with a for loop. Inspect the choice one by one, and store its index once you find the answer.

Sample code (C++):

#include<bits/stdc++.h>

using namespace std;

int main(){
  int n,a,b;
  cin >> n >> a >> b;
  vector<int> c(n);
  for(auto &nx : c){cin >> nx;}
  int ans;
  for(int i=0;i<n;i++){
    if(a+b == c[i]){ans=i+1;break;}
  }
  cout << ans << "\n";
  return 0;
}