#include <iostream>

using namespace std;

const int N = 1e5;

int n;
int a[N];

int main()
{
    scanf("%d", &n);
    for (int i = 1; i <= n; i ++ ) scanf("%d", &a[i]);

    int res;
    for (int i = 1; i < n; i ++ )
        if (a[i] < a[i + 1]) res += a[i + 1] - a[i];

    printf("%d\n", res);

    return 0;
}