r2.cpp

#include <bits/stdc++.h>

using namespace std;

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(0);

    int r1, s, r2;
    cin >> r1 >> s;
    r2 = s * 2 - r1;
    cout << r2 << endl;
    return 0;
}