#include <bits/stdc++.h>
using namespace std;

int asai[] = { 2, 3, 5, 7, 11, 13 };
int bsai[] = { 4, 6, 8, 9, 10, 12 };

void dfs( int a, int b, double x, double &sum ){
  if( a + b == 0 )
    return ( void ) ( sum += x );
  if( a - 1 >= 0 ){
    for( int i = 0; i < 6; ++i )
      return dfs( a - 1, b, x * asai[ i ], sum );
  } else{
    for( int i = 0; i < 6; ++i )
      return dfs( a, b - 1, x * bsai[ i ], sum );
  }
}

signed main(){
  int a, b; cin >> a >> b;
  double ans = 0.0;
  dfs( a, b, 1.0, ans );
  cout << ans / pow( 6, a + b );
  return 0;
}