#include <bits/stdc++.h>

using namespace std;

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

const int Nmax = 1e6 + 5;

int v[Nmax], pozToBeOpened[Nmax];
long long ans;

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

    for(int i = 1; i <= n; ++i)
    {
        pozToBeOpened[i] = max(0, v[i] - v[i - 1]);
        ans += 1LL * pozToBeOpened[i];
    }

    fout << ans;
    return 0;
}