#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    int t;
    cin >> t;
    while (t--) {
        ll n, b;
        cin >> n >> b;
        b = n - b;
        ll l = 0, r = b + 1;
        while (l + 1 != r) {
            ll c = (l + r) / 2;
            if (__int128(b - c) * (c + 1) > __int128(n - c) * c) {
                l = c;
            } else {
                r = c;
            }
        }
        cout << r << endl;
    }
    return 0;
}