#include <iostream>

using namespace std;
int main(void)
{
	int a, Fsum = 0, Tsum = 0, count = 0, count2 = 0;
	int input[100000];
	cin >> a;
	for (int b = 0; b < a; b++) {
		cin >> input[count];
		count++;
		count2++;
	}
	cin >> Fsum;
	count = 0;
	while (count < count2) {
		Tsum += input[count];
		count++;
	}
	cout << Tsum - Fsum << endl;
}