#include <iostream>
#include <cstdio>
using namespace std;
int main()
{
    freopen("operatii.in", "r", stdin);
    freopen("operatii.out", "w", stdout);
    int n, i, x, last;
    cin >> n >> last;
    long long sol=last;
    for(i=1; i<n; i++)
    {
        cin >> x;
        if(x!=0 && x>last) sol+=x-last;
        last=x;
    }
    cout << sol << '\n';
    fclose(stdin);
    fclose(stdout);
    return 0;
}