#include<iostream>
#include<vector>
#include<string>
using namespace std;

int main() {
    
    int N,k,test, solutions;
    solutions = 0;
    cin>>N>>k;
    vector<int> U;
    vector<int> S;
    for(int i=0;i<N;++i) {
        cin>>test;
        if (test == 1) {
            U.push_back(1);
        }
    }

    for (int i = 0; i < (U.size() - 1); ++i) {
        for (int j = 2; j < (k + 1); ++j) {
            if (j + i > U.size()) {
                break;
            }
            solutions++;
        }
    }
    cout << solutions;

    return 0;
 }