import sys

def solve():
    """
    Standard CP format for the Climbing Stairs Problem.
    Input: A single integer n.
    Example: 5
    """
    input_data = sys.stdin.readline().strip()
    if not input_data:
        return
        
    n = int(input_data)

    if n <= 0:
        print("Number of ways = 0")
        return
    if n == 1:
        print("Number of ways = 1")
        return
    if n == 2:
        print("Number of ways = 2")
        return

    # DP with space optimization O(1) space, O(n) time
    prev2 = 1
    prev1 = 2
    
    for _ in range(3, n + 1):
        curr = prev1 + prev2
        prev2 = prev1
        prev1 = curr
        
    print(f"Number of ways = {prev1}")

if __name__ == '__main__':
    solve()