#include <iostream>
#include <fstream>

using namespace std;

int v[1000001], n, i, j;
long long secv;

int main()
{
    ifstream cin ("operatii.in");
    ofstream cout ("operatii.out");
    
    cin >> n;
    
    for ( i = 1; i <= n; i++ ) {
        cin >> v[i];
    }
    for ( i = 1; i < n; i++ ) {
        if ( v[i] < v[i+1] ) {
            secv += (v[i+1]-v[i]);
        }
    }
    
    cout << secv;

    return 0;
}