#include <algorithm>
#include <cmath>
#include <iostream>
#include <numeric>
#include <vector>

int main(void){
    int a, b, c, d;
    std::cin >> a >> b >> c >> d;    
    std::cout << a * d - b * c << std::endl;

    return 0;
}
#include <bits/stdc++.h>
using namespace std;

int main() {
    int A, B; cin >> A >> B;
    cout << (2 * A + 100) - B << endl;
}
