#include <iostream>
using namespace std;
const int N = 1E5 + 10;
typedef long long ll;
ll v[N];
int main(){
    int n;  cin >> n;
    ll res = 0;
    for(int i = 0; i < n; i ++ )    cin >> v[i];
    for(int i = 1; i < n; i ++ ){
        if(v[i] > v[i - 1]) res += v[i] - v[i - 1];
    }
    cout << res << endl;
    return 0;
}