#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;

    long long prev, cur;
    cin >> prev;

    long long ans = 0;

    for(int i = 1; i < n; i++) {
        cin >> cur;
        if(cur > prev) {
            ans += cur - prev;
        }
        prev = cur;
    }

    cout << ans << endl;
    return 0;
}