#include <iostream>
#include <bits/stdc++.h>

using namespace std;

int main()
{
    long long n, k;
    cin >> n >> k;
    bool most;
    long long szam = 0;
    long long bonusz = 0;
    for (int i = 1; i <= n; ++i)
    {
        cin >> most;
        if (most)
        {
            szam++;
        }
    }

    for (int i = 1; i <= szam - k + 1; i++)
    {
        bonusz += i;
    }

    cout << bonusz;

    return 0;
}