Problem: There is a sequence $A = a_0, a_1, ..., a_{n-1}$. You are given the following information and questions.

* relate$(x, y, z)$: $a_y$ is greater than $a_x$ by $z$
* diff$(x, y)$: report the difference between $a_x$ and $a_y$ $(a_y - a_x)$

Constraints

* $2 \leq n \leq 100,000$
* $1 \leq q \leq 200,000$
* $0 \leq x, y < n$
* $x \ne y$
* $0 \leq z \leq 10000$
* There are no inconsistency in the given information

Input


$n \; q$
$query_1$
$query_2$
:
$query_q$


In the first line, $n$ and $q$ are given. Then, $q$ information/questions are given in the following format.


0 $x \; y\; z$


or


1 $x \; y$


where '0' of the first digit denotes the relate information and '1' denotes the diff question.

Output

For each diff question, print the difference between $a_x$ and $a_y$ $(a_y - a_x)$.

Example

Input

5 6
0 0 2 5
0 1 2 3
1 0 1
1 1 3
0 1 4 8
1 0 4


Output

2
?
10

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.*;
import java.util.concurrent.CountDownLatch;
import java.util.logging.Logger;

import javax.sound.midi.MidiMessage;
 
public class Main {
	  static int MAX = 510000;
		static long[] fac=new long[MAX];
		static long[] finv=new long[MAX];
		static long[] inv=new long[MAX];
		static long MOD=(long) (Math.pow(10, 9)+7);
		static boolean[] visited;
	public static void main(String[] args){
		PrintWriter out = new PrintWriter(System.out);
		InputReader sc=new InputReader(System.in);
		int N=sc.nextInt();
		int q=sc.nextInt();
		UnionFindTree uTree=new UnionFindTree(N);
		for (int i = 0; i < q; i++) {
			int c=sc.nextInt();
			if (c==0) {
				int s=sc.nextInt();
				int t=sc.nextInt();
				int x=sc.nextInt();
				uTree.union(s, t, x);
			}
			else {
				int s=sc.nextInt();
				int t=sc.nextInt();
				if (!uTree.same(s, t)) {
					out.println("?");
					continue;
				}
				out.println(uTree.diff(s, t));
				
			}
		}
		out.flush();
	}
	 static class UnionFindTree{
	    	int[] par;
	    	int[] rank;
	    	int[] size;
	    	int[] diff_weight;
	    	int arraysize;
	    	public UnionFindTree(int n) {
	    		this.par=new int[n];
	    		this.rank=new int[n];
	    		this.size=new int[n];
	    		this.diff_weight=new int[n];
	    		arraysize=n;
	    		for (int i = 0; i < arraysize; i++) {
					set(i);
				}
	    	}
	    	public void set(int i) {
	    		par[i]=i;
	    		rank[i]=0;
	    		size[i]=1;
	    		diff_weight[i]=0;
	    	}
	    	public void union(int x,int y,int w) {
	    		w += weight(x); 
	    		w -= weight(y);
	    		int rootx=find(x);
	    		int rooty=find(y);
	    		if (rootx==rooty) {
					return;
				}
	    		if (rank[rootx]>rank[rooty]) {
					par[rooty]=rootx;
					diff_weight[rooty] = w;
					size[rootx]+=size[rooty];
				}
	    		else if (rank[rootx]<rank[rooty]) {
					par[rootx]=rooty;
					w=-w;
					diff_weight[rootx] = w;
					size[rooty]+=size[rootx];
				}
	    		else {
	    			par[rooty]=rootx;
	    			diff_weight[rooty] = w;
	    			rank[rootx]++;
					size[rootx]+=size[rooty];
				}
	    	}
	    	public int find(int x) {
	    		if(par[x] == x) return x;
	    		int r = find(par[x]);
	    		diff_weight[x] += diff_weight[par[x]];
	    		return par[x] = r;
	    	}
	    	public int weight(int x) {
	    		find(x);
	    		return diff_weight[x];
	    	}
	    	public int size(int i) {
	            return size[find(i)];
	        }
	    	public int diff(int x, int y) {
	    		return weight(y) - weight(x);
	    	}
	    	public boolean same(int x, int y) {
	            return find(x) == find(y);
	        }
	    }
	static class InputReader { 
		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;
		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}
 
		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}
 
		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}
 
		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}
 
		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}
 
		public boolean hasNext() {
			skip();
			return hasNextByte();
		}
 
		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
 
		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}
 
		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}
 
		public double nextDouble() {
			return Double.parseDouble(next());
		}
 
		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}
 
		public long[] nextLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}
 
		public char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}
}