#include <iostream>
using namespace std;

const int N = 1e5 + 10;

int prices[N];

int main()
{
    int n;
    cin >> n;
    for(int i = 0;i < n; i++)
        cin >> prices[i];
    
    int retsum = 0;
    for(int i = 1;i < n; i++)
    {
        if(prices[i] - prices[i-1] > 0)
            retsum += (prices[i] - prices[i-1]);
    }
    cout << retsum << endl;
    return 0;
}