/* A */ 
#include <bits/stdc++.h>
using namespace std;
using ll = int64_t;
using pii = pair<int, int>;

const int N = 3;
int n, m, a[N][N];

signed main(int argc, char** argv)
{
	#ifndef ONLINE_JUDGE
		freopen("input.txt", "r", stdin);
	//	freopen("output.txt", "w", stdout);
	#endif
	for (int k = 1; k <= 2; ++k) {
		for (int i = 1; i <= 2; ++i) cin >> a[k][i];
	}
	cout << a[1][1] * a[2][2] - a[1][2] * a[2][1] << endl;
	return 0;	
} 
#include<bits/stdc++.h>
using namespace std;

int main(){
    int A1,A2,A3; cin >> A1 >> A2 >> A3;
    string ans = "No";
    //(A1,A2,A3)
    if(A3-A2 == A2-A1) ans = "Yes";
    //(A1,A3,A2)
    if(A2-A3 == A3-A1) ans = "Yes";
    //(A2,A1,A3)
    if(A3-A1 == A1-A2) ans = "Yes";
    //(A2,A3,A1)
    if(A1-A3 == A3-A2) ans = "Yes";
    //(A3,A1,A2)
    if(A2-A1 == A1-A3) ans = "Yes";
    //(A3,A2,A1)
    if(A1-A2 == A2-A3) ans = "Yes";
    cout << ans << endl;
}
