#include <iostream>

using namespace std;

int main () {
    int a;
    cin >> a;
    int n[a],k[a],br=1;
    for (int i = 0; i < a; i ++) {cin >> n[i];}
    for (int i = 0; i < a; i ++) {
        if (n[i]<n[i+1]) {k[i]=n[i];} else {
                k[i]=n[i];
                br = i; break;}
        ;}
    if (br==0) {cout << 0;} else {cout << k[br]-k[0];}
    return 0;
}