#include <iostream>
#include <bits/stdc++.h>
using ll = long long;
using namespace std;

int main()
{
    ll n, k; cin >> n >> k;
    vector<ll> v(n);
    for (ll i = 0; i < n; i++){
        cin >> v[i];
    }
    ll ans = 0, one = 0;
    for (ll i = 0; i < n; i++){
        if (v[i] == 1) one++;
    }
    for (ll i = 1; i <= one; i++){
        ans += min(one-i, k-1);
    }
    cout << ans;
    return 0;
}