# Author: Steven Carr
# Last Edited: December 2021
# Recusively finds the sum of all the integers until n
import stdio
import sys


# Entry point [DO NOT EDIT].
def main():
    n = int(sys.argv[1])
    stdio.writeln(_sumOfInts(n))


# Returns the sum 1 + 2 + ... + n.
def _sumOfInts(n):
    # Base case: if n equals 1, return 1.
    if n == 1:
        return 1
    # Recursive step: return n plus _sumOfInts(n - 1).
    return n + _sumOfInts(n-1)


if __name__ == '__main__':
    main()