#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define inf 1000000000
#define mod 1000000007
int par[111111],ran[111111],diff_weight[111111];
void init(int n){
	rep(i,n){
		par[i]=i;
		ran[i]=0;
		diff_weight[i]=0;
	}
}
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;
}
int weight(int x){
	find(x);
	return diff_weight[x];
}
bool same(int x,int y){
	return find(x)==find(y);
}
void unite(int x,int y,int w){
	w+=weight(x);
	w-=weight(y);
	x=find(x);
	y=find(y);
	if(x==y)return;
	if(ran[x]<ran[y]){
		swap(x,y);
		w*=-1;
	}
	if(ran[x]==ran[y])ran[x]++;
	par[y]=x;
	diff_weight[y]=w;
}
int diff(int x,int y){
	if(same(x,y))return weight(y)-weight(x);
	return inf;
}
int n,q;
int x,a,b,c;
signed main(){
	cin>>n>>q;
	init(n);
	while(q--){
		cin>>x;
		if(x==0){
			cin>>a>>b>>c;
			unite(a,b,c);
		}
		else{
			cin>>a>>b;
			if(diff(a,b)==inf)puts("?");
			else cout<<diff(a,b)<<endl;
		}
	}
	return 0;
}

