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 cmp(long long int a,long long int b)
{
    if(b>=2*a)
        return 1;
    else
        return 0;
}

int main()
{
    int q;
    long long int n,m;
    long long int s = 0;
    scanf("%lld%lld",&n,&m);
    q = cmp(n,m);
    if(q==0)
    {
        s += m/2+(n-m/2)/2;
        printf("%lld\n",s);
        return 0;
    }
    s += n;
    m -= 2*n;
    n = 0;
    if(m/4==0)
    {
        printf("%lld\n",s);
        return 0;
    }
    s += m/4;
    printf("%lld\n",s);
    return 0;
}