SRM466 div1 medium
class LotteryPyaterochka{ public: double chanceToWin(int N) { double n=N; return (10.0*(5*n-5)*(5*n-6)/2+5*(5*n-5)+1.0)*n*120/((5*n)*(5*n-1)*(5*n-2)*(5*n-3)*(5*n-4)); } };
class LotteryPyaterochka{ public: double chanceToWin(int N) { double n=N; return (10.0*(5*n-5)*(5*n-6)/2+5*(5*n-5)+1.0)*n*120/((5*n)*(5*n-1)*(5*n-2)*(5*n-3)*(5*n-4)); } };