program goat(input,output);
var
 i,j,k:longint;
 s,p:longint;
 ans:longint;
 t:array[0..300000,0..100] of longint;

 begin
 assign(input,'goat.in');
 assign(output,'goat.out');
 reset(input);
 rewrite(output);
 readln(s,p);
 ans:=2140000000;
 for i:=0 to s do
  for j:=0 to p do
   t[i,j]:=210000000;
   t[0,0]:=0;
  for i:=1 to p do
    for j:=1 to s do
    begin
      if (j-5>=0)and(i-2>=0) then
      if t[j-5,i-2]+1<t[j,i] then
      t[j,i]:=t[j-5,i-2]+1;
      if (j-10>=0)and(i-5>=0) then
      if t[j-10,i-5]+1<t[j,i] then
      t[j,i]:=t[j-10,i-5]+1;
      if i+1<=p then
      if t[j-1,i+1]+1<t[j,i]
        then t[j,i]:=t[j-1,i+1]+1;
    end;
  for i:=1 to p do
   if t[s,i]<ans then ans:=t[s,i];
  writeln(ans);
  close(input);
  close(output);
 end.