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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
int main()
{
    int n,m,h=0;
    scanf("%d %d",&n,&m);
    if(2*n<m)
    {
        while(n!=0)
        {
            n=n-1;
            m=m-2;
            h=h+1;
        }
        if(m>=3)
        while(m>0)
        {
            m=m-4;
            h=h+1;
            if(m<4)
            break;
        }
    }
    if(2*n>m)
    {
       while(m>0)
       {
           m=m-2;
           n=n-1;
           h=h+1;
           if(m==1)
            break;
       }
    }
    if(2*n==m&&h==0)
        h=n;
    printf("%d",h);
    return 0;
}