#include <fstream>
#include <cstring>
using namespace std;
ifstream f("operatii.in");
ofstream g("operatii.out");
int n,i,v[1000001],a[1000001];
long long nr;
int main()
{   f>>n;
    for(i=1;i<=n+1;i++){
        f>>v[i];
        a[i]+=v[i]-v[i-1];
    }
    for(i=1;i<=n;i++)
        if(a[i]>0)
            nr+=1ll*a[i];
    g<<nr;
    return 0;
}