'''70. Climbing Stairs
Easy

3866

127

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You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
Example 2:

Input: 3
Output: 3
Explanation: There are three ways to climb to the top.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step'''


n = int(input())
a,b = 1,2
for i in range(n-1):
	a,b = b,a+b
print(a)
'''70. Climbing Stairs
Easy

3866

127

Add to List

Share
You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
Example 2:

Input: 3
Output: 3
Explanation: There are three ways to climb to the top.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step'''


n = int(input())
a,b = 1,2
for i in range(n-1):
	a,b = b,a+b
print(a)
70. Climbing Stairs
 Easy
 
 3866
 
 127
 
 Add to List
 
 Share
 You are climbing a stair case. It takes n steps to reach to the top.
 
 Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
 
 Note: Given n will be a positive integer.
 
 Example 1:
 
 Input: 2
 Output: 2
 Explanation: There are two ways to climb to the top.
 1. 1 step + 1 step
 2. 2 steps
 Example 2:
 
 Input: 3
 Output: 3
 Explanation: There are three ways to climb to the top.
 1. 1 step + 1 step + 1 step
 2. 1 step + 2 steps
 3. 2 steps + 1 step