// viragosret.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <vector>
using namespace std;
int n, i, db,k;
struct adatt
{
    int index, sorszam;
};
int sum;
int main()
{
    
    cin >> n>>k;
    vector<adatt>x;
    for (i = 1; i <= n; ++i)
    {
        int a;
        cin >> a;
        if (a)
        {
            db++;
            x.push_back({ i,db });
        }
    }
    if (k > db)
    {
        cout << 0;
        return 0;
    }
    else
    {
        x.resize(db + 1);
        int a;
        for (i = 0; i <= db; ++i)
        {
             a= i + k;
             if (a > db) break;
            sum += (db - a) + 1;
        }
        cout << sum;
    }
    return 0;
}
/*
10 3
0 1 1 0 0 0 1 1 0 1


*/
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// Debug program: F5 or Debug > Start Debugging menu

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