#include <iostream>
#include <cmath>
using namespace std;
double downhillLength(int h, int r) {
double ratio = (double)h / r;
double downhill = sqrt(2 * r * h - h * h);
return downhill;
}
int main() {
int t;
cin >> t;
for (int i = 0; i < t; ++i) {
int h, r;
cin >> h >> r;
// Kiểm tra điều kiện hợp lệ
if (h <= r) {
cout << "Invalid test case" << endl;
} else {
double result = downhillLength(h, r);
cout << fixed << result << endl;
}
}
return 0;
}
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