dp[i] = dp[i-1] + dp[i-2]
n = int(input()) dp = [0] * (n+2) dp[0], dp[1] = 0, 1 if n <= 1 : print(n) else : for i in range(2, n+1): dp[i] = dp[i-1] + dp[i-2] print(dp[n])