#include <iostream>
#include <queue>
#define ll long long

using namespace std;

int rek(ll n)
{
    if (n == 0)
        return 0;
    return n + rek(n - 1);
}

ll db;
int main()
{
    ll n, m, k;
    cin >> n >> m;
    vector <ll> a;
    for (ll i = 1; i <= n; ++i)
    {
        cin >> k;
        if (k == 1)
            a.push_back(k);
    }
    ll koz;
    for (ll i = 0; i < a.size(); ++i)
    {
        koz = a.size() / 2 + i;
        for (ll j = koz; j < a.size(); ++j)
            ++db;
    }
    if (db >= m)
        cout << db;
    else
        cout << "0";

    return 0;
}