#include <bits/stdc++.h>

using namespace std;

// A random variable, X, follows Poisson distribution with mean of
// 2.5. Find the probability with which the random variable is equal
// to 5.

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    double lambda = 2.5;
    int k = 5;
    
    // P(k=5, lambda = 5)
    double probability = pow(lambda,k) * pow(M_E, -lambda)/(5*4*3*2);
    cout << fixed << setprecision(3) << probability << endl;
    return 0;
}