#k402. 費氏數列
n = int(input())
if n>2:
    n-=2
else:
    if n==1:
        print(0)
    else:
        print(0,1)
nums = [0,1]
for i in range(n):
    nums.append(nums[i]+nums[i+1])
total = nums[-1]
print(total)