#include <iostream>
#include <fstream>
using namespace std;

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