#include <iostream>
#include <fstream>

using namespace std;

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

const int NMAX = 1000003, VMAX = 100003;
int n, v[NMAX], scoase = 0;

int main() {

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

        if (v[i] == 0)
            scoase++;
    }

    int res = 0;
    while (scoase < n) {
        for (int i = 1; i <= n; i++) {
            if (v[i + 1] == 0 && v[i] > 0) {
                res++;
            }

            if (v[i] != 0) {
                v[i]--;
                if (v[i] == 0)
                    scoase++;
            }
        }
    }

    fout << res;



    return 0;
}