lca,difference array on tree

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
vector<vector<int>>g;
const int N=1e5;
const int mxe=22;
int up[N][mxe];
vector<int>par,dep,diff;
vector<ll>ans;
void dfs(int vert,int p=0,int d=0){
    par[vert]=p;
    dep[vert]=d;
    for(auto&child:g[vert]){
        if(child!=p){
            dfs(child,vert,d+1);
        }
    }
}
int lift(int vert,int dist){
    int node=vert;
    for(int i=mxe-1;i>=0;i--){
        if(node!=0){
            if(dist&(1<<i)){
                node=up[node][i];
            }
        }
    }
    return node;
}
int lca(int u,int v){
    u=lift(u,dep[u]-min(dep[u],dep[v]));
    v=lift(v,dep[v]-min(dep[u],dep[v]));
    if(u==v)return u;
    for(int i=mxe-1;i>=0;i--){
       if(up[u][i]!=up[v][i]){
          u=up[u][i];
          v=up[v][i];
       }
    }
    return up[u][0];
}
ll dfs1(int vert,int p){
    ll sum=1ll*diff[vert];
    for(auto&child:g[vert]){
        if(child!=p){
            sum+=dfs1(child,vert);;
        }
    }
    return ans[vert]=sum;
}
void solve(){
  int n,k;cin>>n>>k;
  par.resize(n+1,0);
  dep.resize(n+1,0);
  diff.resize(n+2,0);
  ans.resize(n+1,0);
  g.resize(n+1,vector<int>());
  for(int i=0;i<n-1;i++){
    int u,v;cin>>u>>v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  memset(up,0,sizeof(up));
  dfs(1,0,0);
  for(int i=1;i<=n;i++){
    up[i][0]=par[i];
  }
  for(int i=1;i<mxe;i++){
    for(int j=1;j<=n;j++){
        if(up[j][i-1]!=0){
            up[j][i]=up[up[j][i-1]][i-1];
        }
    }
  }
  for(int i=0;i<k;i++){
    int u,v;cin>>u>>v;
    int l=lca(u,v);
   // cout<<l+1<<endl;
   diff[u]++;diff[v]++;diff[l]--;diff[par[l]]--;
  }
  dfs1(1,0);
  ll res=0;
  for(int i=1;i<=n;i++){
    res=max(ans[i],res);
  }
  cout<<res;
}
int main() {
// freopen("haybales.in","r",stdin);
// freopen("haybales.out","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t=1;
   // cin>>t;
    while(t--){
        solve();
    }
    return 0;
}
//  for(int l=1;l<me;l++){
 //   for(int i=0;i<n;i++){
 //  if(up[i][l-1]!=-1)up[i][l]=up[up[i][l-1]][l-1];
//   }
// }
/*
  lift code:
   int lift(int node,int distance){
    for(int e=0;e<maxe;e++){
     if(node!=-1){
      if(distance&(1<<e)){
       node=up[node][e];
      }
     }
    }
    return node;
   }
*/
//