#include <bits/stdc++.h>
using namespace std;

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

int n, a, b;

int main()
{
    fin>>n>>a;
    int sol=0;
    for(int i=2;i<=n;++i){
      fin>>b;
      if(a<b) sol+=(b-a);
      a=b;
    }
    fout<<sol<<"\n";
    return 0;
}