知识点：运算 

#include <iostream>
using namespace std;

int main() {
    int a = 0;
    int b = 0;
    int c = 0;
    int d = 0;
    int result = 0;

    cin >> a >> b >> c >> d;

    result = (a + b - c) * d;

    cout << result << endl;

    return 0;
}