def fibonacci_no_rec(n): # 0 1 动态规划算法 if n <= 0: return 0 elif n == 1: return 1 else: fib = [0, 1] for i in range(2, n+1): fib.append(fib[i-1] + fib[i-2]) return fib[n] n = int(input()) result = fibonacci_no_rec(n) print(result)