干就完事了

#include <iostream>

using namespace std;

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n, res;
    cin >> n;
    int a;
    cin >> a;
    for (int i = 1; i < n; i ++)
    {
        int b;
        cin >> b;
        if (a < b) res += b - a;
        a = b;
    }
    cout << res << endl;

    return 0;
}