# Author: Steven Carr
# Last Edited: October 2021
# Computes the fibonacci sequence up to the n number
import stdio
import sys
# User input
n = int(sys.argv[1])
# The first three numbers in the fibonacci sequence
a = 1
b = 1
i = 3
# Infinitely repeat loop if i <= n is true to continue
# the fibonacci sequence to the place of uer input n.
# Otherwise, break the loop
while True:
    if i <= n:
        t = b
        b = a + b
        a = t
        i += 1
    else:
        break
# Output the number of the fibonacci sequence
stdio.writeln(b)