def fib(n):                                                                                                     
    if n <= 0:                                                                                                        
        return 0                                                                                                      
    elif n == 1:                                                                                                      
        return 1                                                                                                      
                                                                                                                        
    a, b = 0, 1                                                                                                       
    for _ in range(2, n + 1):                                                                                         
        a, b = b, a + b                                                                                               
    return b
      
print(fib(23))