def fib(n):
    if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b    

print(fib(int(input())))
 def fib(n):
    if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b     fib if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b     n==0 n 0 return 1 1 elif n==1:
        return 1
     n==1 n 1 return 1 1 a,b=1,2 a 1 b 2 for i in range(n-2):
            a,b=b,a+b
         i range(n-2) range n-2 n 2 a,b=b,a+b a b b a+b a b return b b n n print(fib(int(input()))) print fib(int(input())) fib int(input()) int input() input def fib(n):
    if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b     def fib(n):
    if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b     fib
def fib(n):
    if n==0:
        return 1
    elif n==1:
        return 1
    else:
        a,b=1,2
        for i in range(n-2):
            a,b=b,a+b
        return b    

print(fib(int(input())))

