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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main {
	public static void main(String[] args) throws IOException {
		proconScan proScan = new proconScan(" ");
		proScan.scan();
		long nInteger = proScan.nextInteger();
		long mInteger = proScan.nextInteger();
		nInteger*=2;
		long buf = nInteger + mInteger;
		System.out.println((int)Math.ceil(buf/4));
		proScan.proconEnd();
	}
 
}
 
 
class proconScan {
	private BufferedReader br;
	private String inLine;
	private String[] inString;
	private Integer idx;
	private String splitChar;
 
	public proconScan() {
		br = new BufferedReader(new InputStreamReader(System.in));
		idx = 0;
		splitChar = " ";
	}
 
	public proconScan(String split) {
		br = new BufferedReader(new InputStreamReader(System.in));
		idx = 0;
		splitChar = split;
	}
 
	public void proconEnd() throws IOException {
		// TODO 自動生成されたメソッド・スタブ
		br.close();
	}
 
	public String scan() throws IOException {
		idx = 0;
		inLine = br.readLine();
		inString = inLine.split(splitChar, 0);
		return inLine;
	}
 
	public Integer scanInteger1() throws IOException {
		scan();
		return Integer.parseInt(inString[0]);
	}
 
	public String backLine() {
		return inLine;
	}
 
	public String nextString() {
		return inString[idx++];
	}
 
	public String[] getString() {
		return inString;
	}
 
	public Integer nextInteger() {
		Integer num;
		try {
			num = Integer.parseInt(inString[idx++]);
		} catch (NumberFormatException e) {
			num = null;// TODO: handle exception
		}
		return num;
	}
 
	public Integer[] getInteger() {
		Integer[] num = new Integer[this.getLen()];
 
		for (int i = 0; i < this.getLen(); i++) {
			num[i] = Integer.parseInt(inString[i]);
		}
 
		return num;
	}
 
	public Float nextFloat() {
		Float num;
		try {
			num = Float.parseFloat(inString[idx++]);
		} catch (NumberFormatException e) {
			num = null;// TODO: handle exception
		}
		return num;
	}
 
	public Float[] getFloat() {
		Float[] num = new Float[this.getLen()];
 
		for (int i = 0; i < this.getLen(); i++) {
			num[i] = Float.parseFloat(inString[i]);
		}
 
		return num;
	}
 
	public Integer getLen() {
		return inString.length;
	}
 
	public int[] getInt() {
		int[] num = new int[this.getLen()];
 
		for (int i = 0; i < this.getLen(); i++) {
			num[i] = Integer.parseInt(inString[i]);
		}
 
		return num;
	}
 
}