#include <fstream>

using namespace std;

int main()
{
    int n, ex, actual, sol = 0;
    ifstream in("operatii.in");
    in>>n>>ex;
    for(int i = 2; i <= n; i++)
    {
        in>>actual;
        if(actual > ex) sol += actual - ex;
        ex = actual;
    } in.close();
    ofstream out("operatii.out"); out<<sol;
    out.close();
    return 0;
}