<reponame>KATO-Hiro/AtCoder
# -*- coding: utf-8 -*-


def main():
    r1, r2 = map(int, input().split())
    print(r1 * r2 / (r1 + r2))


if __name__ == '__main__':
    main()

# -*- coding: utf-8 -*-


def main():
    r1, r2 = map(int, input().split())
    print(r1 * r2 / (r1 + r2))


if __name__ == '__main__':
    main()
# -*- coding: utf-8 -*-