Problem:
Score : 300 points

Problem Statement

Snuke loves puzzles.

Today, he is working on a puzzle using S- and c-shaped pieces.
In this puzzle, you can combine two c-shaped pieces into one S-shaped piece, as shown in the figure below:

Snuke decided to create as many Scc groups as possible by putting together one S-shaped piece and two c-shaped pieces.

Find the maximum number of Scc groups that can be created when Snuke has N S-shaped pieces and M c-shaped pieces.

Constraints

1 ≤ N,M ≤ 10^{12}

Input

The input is given from Standard Input in the following format:

N M

Output

Print the answer.

Sample Input 1

1 6

Sample Output 1

2

Two Scc groups can be created as follows:

Combine two c-shaped pieces into one S-shaped piece

Create two Scc groups, each from one S-shaped piece and two c-shaped pieces

Sample Input 2

12345 678901

Sample Output 2

175897

Solution in Pascal (FPC 2.6.2) (judge verdict: Wrong Answer)

var
 n,m,i:longint;
begin
 readln(n,m);
 while (n>0) or (m>1) do
  begin
   inc(i);
   if n=0 then m:=m-2
              else dec(n);
   if m>=2 then m:=m-2
                  else n:=n-1;
  end;
 if (n<0) or (m<0) then dec(i);
 writeln(i);
end.