斐波那契数列 Python

def fibonacci(n):
    if n==1 or n==2:
        return 1
    else:
        return fibonacci(n-1)+fibonacci(n-2)
n=int(input())
print(fibonacci(n))

def fibonacci(n):
    if n==1 or n==2:
        return 1
    else:
        a=b=1
        for i in range(3,n+1):
            s=a+b
            a=b
            b=s
        return s
n=int(input())
print(fibonacci(n))