#include <bits/stdc++.h>
using namespace std;

// prefix sum, and result += sum - k + 1 if sum >= k

long long n, k, ans;
vector<int> can_harvest;
vector<int> vec;

int main()
{
    cin >> n >> k;
    can_harvest.assign(n + 1, 0);
    vec.assign(n + 1, 0);
    for (int i=1; i <= n; i++) {
        cin >> can_harvest[i];
        vec[i] = can_harvest[i] + vec[i - 1];
        if (vec[i] >= k && can_harvest[i]) {
            ans += vec[i] - k + 1;
        }
    }
    cout << ans << '\n';
    return 0;
}