text: '''
  Nth Fibonacci Number
  
  Nth term of Fibonacci series F(n) is calculated using the following formula -
      F(n) = F(n-1) + F(n-2), 
      Where, F(1) = F(2) = 1
  Provided N you have to find out the Nth Fibonacci Number.
  
  Input Format :
  The first line of each test case contains a real number ‘N’.
  
  Output Format :
  For each test case, return its equivalent Fibonacci number.
  
  Constraints:
  1 <= N <= 10000     
  Where ‘N’ represents the number for which we have to find its equivalent Fibonacci number.
  
  Time Limit: 1 second
  
  Sample Input 1:
  6
  
  Sample Output 1:
  8
  
  Explanation of Sample Input 1:
  Now the number is ‘6’ so we have to find the “6th” Fibonacci number
  So by using the property of the Fibonacci series i.e 
  [ 1, 1, 2, 3, 5, 8]
  So the “6th” element is “8” hence we get the output.
  '''
  
  ## Read input as specified in the question.
  ## Print output as specified in the question.
  
  n = int(input())
  a = 0
  b = 1
  i=2
  while i <= n: 
  	c = a + b
  	a = b
  	b = c
  	i += 1
  print(b)