#include <iostream>
#include <fstream>
#define NMAX 1000000

using namespace std;

ifstream f("operatii.in");
ofstream g("operatii.out");

int n, v[NMAX+10];
long long sol;

int main()
{
    f >> n;
    for(int i=1; i<=n; i++) f >> v[i];
    int i = 1, val = 0, maxi = 0;
    v[n+1] = 0;
    n++;
    while(i <= n)
        {   maxi = max(maxi, v[i]);
            if(v[i] < maxi)
                {   sol = sol + (long long)maxi - (long long)val;
                    val = v[i+1];
                    maxi = 0;
                }
            i++;
        }
    g << sol << '\n';
    return 0;
}