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>

int main()
{
	unsigned long long int ans = 0ULL;
	
	unsigned long long int n;
	unsigned long long int m;
	scanf( "%llu %llu", &n, &m );
	
	unsigned long long int cc_m = (unsigned long long int)( m / 2ULL );
	
	unsigned long long int scc_org = 0ULL;
	if ( n < cc_m )
	{
		scc_org = n;
	}
	else
	{
		scc_org = cc_m;
	}
	
	unsigned long long int r_c_m = (unsigned long long int)( m - cc_m );
	unsigned long long int scc_m = (unsigned long long int)( r_c_m / 4ULL );
	
	ans = (unsigned long long int)( scc_org + scc_m );
	
	printf( "%llu\n", ans );
	
	return 0;
}