#!/usr/bin/env python3
import sys
import random

rng = random.SystemRandom()

def secret_santa(names):
    """Draw pairings for secret santa.

    We recognize the problem as a random Hamiltonian cycle
    on the complete graph formed by the set of names.
    """
    g = list(names)
    rng.shuffle(g)
    return list(zip(g, g[1:] + g[:1]))

if __name__ == '__main__':
    for pair in secret_santa(sys.argv[1:]):
        print("%s -> %s" % pair)