#include <iostream>
#include <fstream>


using namespace std;

ifstream fin("operatii.in");
ofstream fout("operatii.out");

int v[1000005];
int n;
int main()
{
    fin >> n;
    for (int i=0; i<n; i++) {
        fin >> v[i];
    }
    long long cnt=0;
    for (int i=0; i<n-1; i++) {
        if (v[i] < v[i+1]) cnt += v[i + 1] - v[i];
    }
    fout << cnt;
    return 0;
}