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

int main () {
    int n,r=0,x,y;
    ifstream I("operatii.in");
    ofstream O("operatii.out");
    I>>n;
    I>>x;
    for (int i=2;i<=n;i++) {
        I>>y;
        
        if (x-y >= 0)
            r=r+x-y;
            
        x=y;
    }
    O<<r+y;
}