#include <fstream>

using namespace std;

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

const int DIM = 1000001;
int v[DIM];

int main() {
    int n;
    fin >> n;

    long long sol = 0;
    for (int i = 1; i <= n; i++) {
        fin >> v[i];

        if (v[i] != 0 && v[i] > v[i - 1])
            sol += v[i] - v[i - 1];
    }

    fout << sol;

    return 0;
}