Shared code

//based on lowest common ancestor
//problem link https://cses.fi/problemset/task/1135
#include<bits/stdc++.h>
using namespace std;
const int LOG=20;
#define int long long
vector<vector<int>> up;
vector<int> depth;

void dfs(int node ,int parent, vector<int>tree[]){
    for(int nbr:tree[node]){
        if(nbr==parent ) continue;

        up[nbr][0]=node;


        depth[nbr]= depth[node]+1;
        
        for(int j=1;j<LOG;j++){
            up[nbr][j]= up[ up[nbr][j-1] ][j-1];
        }

        dfs(nbr,node,tree);
    }
    return ;
}


int get_LCA(int u,int v){
    if(depth[u]< depth[v])
        swap(u,v);
    int k=depth[u]-depth[v];

    if (k!=0){
        for(int i=LOG-1;i>=0;i--){
        if(k >= (1<<i)){
            u=up[u][i];
            k=k-(1<<i);
        }
            
    }
    }
    
    
    if(u==v) return u;

    for(int j=LOG-1;j>=0;j--){
        if(up[u][j]!= up[v][j]){
            u=up[u][j];
            v=up[v][j];
        }
    }
    return up[u][0];
}
signed main(){
    #ifndef ONLINE_JUDGE

	freopen("input.txt", "r", stdin);

	freopen("output.txt", "w", stdout);

    #endif
    int n,q;
    cin>>n>>q;
    up.resize(n+1,vector<int>(LOG,0));
    
    depth.resize(n+1,0);
    vector<int> tree[n+1];
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        tree[a].push_back(b);
        tree[b].push_back(a);
    }
    
    dfs(1,0,tree);
    

    while(q--){
        int a,b;
        cin>>a>>b;
        int LCA= get_LCA(a,b);
        cout<< abs(depth[a]+ depth[b]- 2* depth[LCA] )<<endl;

    }
    
}