clim2

import sys


# Input: n is an int of how many climbing holds there are
# Output: return an integer of how many distinct ways there are to reach the last hold (order matters)
def distinct_ways(n):
    n1 = 1
    n2 = 2
    if (n == 1):
        return 1
    elif (n == 2):
        return 2
    else:
        for i in range(2, n):
            n3 = n1 + n2
            n1 = n2
            n2 = n3
        return n3


def main():

    # read number of holds
    n = int(input())

    # get the result from your call to distinct_ways()
    result = distinct_ways(n)
    # print the result to standard output
    print(result)


if __name__ == "__main__":
    main()