#include <fstream>
using namespace std;

int main()
{
    long long i,n,x,y,s=0;
    ifstream in ("operatii.in");
    ofstream out ("operatii.out");
    in>>n>>x;
    for (i=1;i<=n;i++)
    {
        in>>y;
        if (x-y>=0)
        s+=x-y;
        x=y;
    }
    out<<s+y;
    return 0;
}