#include <fstream>

using namespace std;

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

int v[1000050], n;

int main()
{
    f >> n;
    long long k = 0;
    for(int i = 1; i <= n; i++)
         f >> v[i];
    for(int i = 1; i <= n; i++)
    {
        if (v[i] >= v[i-1])
        k = k + v[i] - v[i-1];
    }
    g << k;
    return 0;
}