#include<iostream>
#include<vector>
using namespace std;
int main() {
    int N;
    cin >> N;
    int m = 0;
    vector<int>a(N);
    for (int i = 0; i < N; i++)cin >> a[i];
    for (int i = 1; i < N; i++) {
        m=a[i]-a[i-1]
    }
    cout << m << endl;
    return 0;
}