#!/usr/bin/env python3

import scipy.optimize


c = [-1000, -2000]
A = [[3 / 4, 2 / 7], [1 / 4, 5 / 7]]
xb = (0, None)
yb = (0, None)


def main():
    b = [int(x) for x in input().split()]
    res = scipy.optimize.linprog(c, A_ub=A, b_ub=b, bounds=(xb, yb))
    print("{:.12f}".format(-res.fun))


if __name__ == '__main__':
    main()