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 PYTHON3):

Solution:
# N,M = map(int,sys.stdin.readline().split())
# a = tuple(map(int,sys.stdin.readline().split())) # single line with multi param
# a = tuple(int(sys.stdin.readline()) for _ in range(N)) # multi line with single param
# a = tuple(tuple(map(int,sys.stdin.readline().rstrip().split())) for _ in range(N)) # multi line with multi param
# s = sys.stdin.readline().rstrip()
# N = int(sys.stdin.readline())
# INF = float("inf")

import sys
sys.setrecursionlimit(1000000)
N,Q = map(int,sys.stdin.readline().split())
qs = tuple(tuple(map(int,sys.stdin.readline().rstrip().split())) for _ in range(Q)) # multi line with multi param

parents = list(range(N))
diffs = [0]*N

def root(x):
    if parents[x]==x:
        return x
    else:
        pr = root(parents[x])
        diffs[x] += diffs[parents[x]]
        parents[x] = pr
        return pr

def weight(x):
    root(x)
    return diffs[x]

def diff(x,y):
    return weight(y)-weight(x)

def issame(x,y):
    return root(x) == root(y)

# make sure weight(y)-weight(x)=w
def merge(x,y,w):
    # assume ry > rx
    rx = root(x)
    ry = root(y)
    # incase rx!=x and ry !=y
    diff = weight(x)+(w-weight(y))
    if rx == ry:
        return False
    if rx < ry:
        rx,ry,diff = ry,rx,-diff
    diffs[ry] = diff
    parents[ry] = rx
    return True

for q in qs:
    if q[0]==0:
        x,y,z = q[1:]
        merge(x,y,z)
    else:
        x,y = q[1:]
        if root(x)==root(y):
            print(diff(x,y))
        else:
            print("?")