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

    
    return 0;
}