#include <fstream>
#include <iostream>
#include <algorithm>

using namespace std;
ifstream in("operatii.in");
ofstream out("operatii.out");
int n,c,cmax;
long long int nr;
int main()
{
   in>>n;
   in>>cmax;
   nr=cmax;
   for(int i=2;i<=n;i++)
   {
       in>>c;
       if(c>cmax)
           nr=nr+c-cmax;
       cmax=c;
   }
   out<<nr;
}