#
# µû¶óÇÏ¸ç ¹è¿ì´Â ÆÄÀ̽ã°ú µ¥ÀÌÅÍ°úÇÐ(»ý´ÉÃâÆÇ»ç 2020)
# LAB 6-7 ÇǺ¸³ªÄ¡ ÇÔ¼ö °è»êÇϱâ, 164ÂÊ
#
def fibonacci(n):
if n < 2:
return n
a, b = 0, 1
for _ in range(n-1):
a, b = b, a + b
return b
i = int(input("¸î ¹ø° Ç×: "))
print(fibonacci(i-1))