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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>

int main(int argc, const char * argv[]) {

    
    long N,M,ans; //S,c
    scanf("%ld",&N);
    scanf("%ld",&M);
    
    //Sのが大きい?
    if(M/4 > N + (M-N)/4){
        printf("%ld\n",M/4);
    }else
    if(N>2*M){
        ans = M/2;
        printf("%ld\n",ans);
    }else{
        ans = N;
        M -= N*2;

        if(M>=4){
            ans += M/4;
        }
        printf("%ld\n",ans);
    }

    
//    printf("%ld\n",power%discount);
    return 0;
}