#include <bits/stdc++.h>

using namespace std;


int main()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);

    int N, crt, ant;

    scanf("%d", &N);
    ant = 0;
    long long total = 0;
    for(int i = 1; i <= N; ++i)
    {
        scanf("%d", &crt);
        if(crt > ant && crt != 0)
           total += crt - ant;
        ant = crt;
    }
    printf("%lld\n", total);

    return 0;
}