#include <bits/stdc++.h>
#define nmax 1000005

using namespace std;

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

int n;
int a[nmax];

int main()
{
    int i, s, cnt;
    fin >> n;
    s = 0;
    for(i = 1; i <= n; i++)
    {
        fin >> a[i];
        s += a[i];
    }
    cnt = 0;
    while(s > 0)
    {
        cnt++;
        for(i = 1; i <= n ; )
        {
            while(a[i] == 0)    i++;
            while(a[i] != 0)
            {
                s--;
                a[i]--;
                i++;
            }
            i = n + 2;
        }
    }
    fout << cnt;
    return 0;
}