#include <iostream>
#include <cmath>
using namespace std;

// constant number 'e'
const double Euler = std::exp(1.0);

// return x^y
int power(int x, int y){
    if(y == 0 && x != 0) return 1;
    int i, z = x;   
    for(i = 0; i < y; i++)
        z *= z;

    return z;
}

// factorial of integer x
int fact(int x){
    if(x == 0) return 1;
    
    int i, factorial = 1;
    for(i = 1; i <= x; i++)
        factorial *= i;

    return factorial;
}

int main(){
    // P{N = n} = Λ^n * e^-Λ / n!
    // n: number of blocks to find within given time frame
    // Λ or lambda: number of blocks you would expect to find in 10 minutes

    int n = 3, lambda = 1;
    double P = power(lambda, n) * pow(Euler, -lambda) / fact(n);
    
    cout << P << endl;
}

For n=3, Λ=1, P=0.0613132
For n=4, Λ=1, P=0.01532830
For n=5, Λ=1, P=0.00306566
For n=6, Λ=1, P=0.000510944
For n=7, Λ=1, P=0.00000729

{Total of even integers from 1 to 6} / {Total integers from 1 to 6} = 3 / 6 = 0.5