#include <iostream>
#include <fstream>

using namespace std;

ifstream fin ("operatii.in");
ofstream fout ("operatii.out");

int main()
{
    long long n,kon=0,i,a,b,s=0;
    fin>>n;
    fin>>a;
    for(i=2;i<=n;i++)
    {
        fin>>b;
        s=0;
        if(a<b)
           s=b-a;
        kon+=s;
        a=b;
    }
    fout <<kon;
    return 0;
}