---

#include <iostream>
using namespace std;

int main() {
    long long n, k;
    cin >> n >> k;

    unsigned long long lo = 0, hi = 3200000000ULL; 
    while (lo < hi) {
        unsigned long long mid = (lo + hi + 1) / 2;
        if (mid * (mid + 1) / 2 <= (unsigned long long)k) lo = mid;   
        else hi = mid - 1;
    }

    long long t = lo;
    if (t > n) t = n;         
    cout << t << "\n";
    return 0;
}