def fibonacci(n):

    # Write your code here.
    a=0
    b=1
    k.append(a)
    k.append(b)
    while(n+2>0):
        c=a+b
        a=b
        b=c
        k.append(c)
        n-=1

n = int(input())
k=[]
fibonacci(n)
print(k[n])