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OI-codes/Codeforces/1612/C/C.cpp

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#include <bits/stdc++.h>
using namespace std;
int t, k;
long long x, ans;
inline long long calc(long long d) {
return (d + 1) * d / 2;
}
inline long long calc2(long long d) {
return (k * 2 - d + 1) * d / 2;
}
int main() {
cin >> t;
while (t--) {
cin >> k >> x;
long long l = 0, r = k;
while (l < r) {
int mid = l + r + 1 >> 1;
if (calc(mid) <= x) {
l = mid;
} else {
r = mid - 1;
}
}
if (r < k) {
ans = r + (calc(r) < x);
cout << min(ans, k * 2ll - 1) << endl;
continue;
}
x -= (k - 1ll) * k / 2ll;
l = 0;
r = k;
while (l < r) {
int mid = l + r + 1 >> 1;
if (calc2(mid) <= x) {
l = mid;
} else {
r = mid - 1;
}
}
ans = (r + k - 1 + (calc2(r) < x));
cout << min(ans, k * 2ll - 1) << endl;
}
return 0;
}