#define _CRT_SECURE_NO_WARNINGS #define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; int main() { double C; double Rin, Rout; double r1, r2; double res; cin >> C >> Rin >> Rout; r1 = (Rout - Rin) / 2; r2 = (Rout - Rin) / 2 + Rin; res = (r1 * r1 * M_PI) * (M_PI * r2 * 2) * C; cerr << fixed << setprecision(10) << res << endl; cout << "Hello World!" << endl; return (0); }