Possion random variable

#include <bits/stdc++.h>
using namespace std;
float poisson(int x, int y)
{
    if (y == 0)
        return pow(2.718281828, (-x));
    else
    {
        return ((float)x / y) * poisson(x, y - 1);
    }
}
int main()
{
    int x, y;
    cout << "Enter the value of x and lambda reopectively: \n";
    cin >> x >> y;
    float ans = poisson(x, y);
    cout << "The result is: \n"
         << ans;
}