def fac_naive_recursive(n):
    if n <= 1: return 1
    return n * fac_naive_recursive(n-1)  

def fac_tail_recursive(n, a=1):
    if n < 1: return a 
    return fac_tail_recursive(n-1, a*n)   

def fac_for_loop(n, a=1):
    for i in range(1, n+1):
        a = a*i 
    return a

def fac_while_loop(n, a=1):
    while True:
        if n < 1: return a
        a = a*n 
        n = n-1 

def fac_while_loop_2(n, a=1):
    while not n < 1:
        a = a*n 
        n = n-1 
    return a    

print(fac_naive_recursive(5))
print(fac_tail_recursive(5))
print(fac_for_loop(5))
print(fac_while_loop(5))
print(fac_while_loop_2(5))