#include <fstream>
using namespace std;
ifstream f("operatii.in");
ofstream g("operatii.out");

int N,prec,curent;
unsigned long long sol;
int main()
{
    f>>N;
    for(int i=1;i<=N;++i)
    {
        f>>curent;
        if(curent>prec)sol+=(curent-prec);
        prec=curent;
    }
    g<<sol<<'\n';
    f.close();g.close();
    return 0;
}