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(void){

  long long int N,M,i;
  scanf("%lld %lld",&N,&M);

  long long int count1,count2;
  long long int answer;
  count1 = 0;
  for(i=0;i<M/2;i++){
    if((M<=0)||(N<=0)){
      break;
    }else{
      M = M-2;
      N = N-1;
      count1++;
    }
  }
  count2 = M/4;

  answer = count1 + count2;
  printf("%lld\n",answer);

  return 0;
}