/* -*- coding: utf-8 -*-
 *
 * 453.cc: No.453 製薬会社 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

typedef long double ld;

const ld DELTA = 1.0e-12;

/* typedef */

/* global variables */

/* subroutines */

ld price(ld a, ld c, ld d) {
  ld c0 = c - a * 3 / 4;
  ld d0 = d - a / 4;
  ld b = min(c0 * 7 / 2, d0 * 7 / 5);
  return a + b * 2;
}

/* main */

int main() {
  ld c, d;
  cin >> c >> d;

  ld maxa = min(c * 4 / 3, d * 4);

  ld la = 0.0, ra = maxa;
  while (la + DELTA < ra) {
    ld a0 = (la * 2 + ra) / 3;
    ld a1 = (la + ra * 2) / 3;
    if (price(a0, c, d) < price(a1, c, d)) la = a0;
    else ra = a1;
  }

  printf("%.9Lf\n", price(ra, c, d) * 1000);
  return 0;
}