#include <iostream>
#include <fstream>
#include <cmath>
#define PI 3.14159265358979323846
using namespace std;

#ifndef ONLINE_JUDGE
    #define cin fin
    ifstream fin("input");
#endif

double N, R;

int main() {
    cin >> N >> R;
    N /= 2.0;

    if (R <= N) {
        cout << PI * R * R << '\n';
        return 0;
    }
    if (R >= N * sqrt(2.0)) {
        cout << 4.0 * N * N << '\n';
        return 0;
    }

    double A, B, C;
    A = N;
    C = R;
    B = sqrt(C * C - A * A);
    double angle = 90.0 - (acos(A / C) * 180.0 / PI) * 2.0;

    printf("%.3lf\n", 4.0 * (A * B + PI * R * R * angle / 360.0));
}

This program works fine on all the tests I saw on the forum. But I get WA #1 probably because of the wrong precision. I printed the value with 4 and 6 decimals but I get the same WA #1.
Could anyone tell me please how can I solve the "error" ? It's annoying to have a good solution and take WA.
Thanks a lot!


LATER EDIT:
It seems I succeeded with such a function:

inline void precise(double X, const int &decimals) {
    cout << (int)(X);
    cout << '.';
    X = X - (int)(X);
    for (int i = 1; i <= decimals; ++i) {
        X = X * 10.0;
        cout << (int)(X);
        X = X - (int)(X);
    }
    cout << '\n';
}

...

precise((double)(4.0 * (A * B + PI * R * R * angle / 360.0)), 3);

Have fun!

Edited by author 25.01.2014 04:19