3046. R2

c
#include <bits/stdc++.h>

using namespace std;

int main(){
    cin.tie(NULL);
    cout.tie(NULL);
    ios_base::sync_with_stdio(false);
    
    int R1, R2, S;
    cin >> R1 >> S;

    R2 = S * 2 - R1;

    cout << R2 << "\n";

    return 0;
}```