#include <fstream>
using namespace std;
ifstream fin("operatii.in");
ofstream fout("operatii.out");
int n,v[1000000],x;
long long s;
int main()
{
    int i;
    fin>>n;
    for(i=1; i<=n; i++)
        fin>>v[i];
    i=1;
    while(i<=n)
    {
        if(v[i]!=0)
        {
            while(v[i]!=0)
            {
                v[i]--;
                i++;
            }
            i=x;
            s++;
        }
        else
        {
            x=i;
            i++;
        }
    }
    fout<<s;
}