#include <bits/stdc++.h>
using namespace std;
void solve(){
    int n,jk,tk,k;
    cin>>n>>jk>>tk>>k;
    vector<vector<int>> g;
    g.resize(n+1,vector<int>());
    for (int i=0; i<n-1;i++){
        int a,b;
        cin>>a>>b;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    vector<int> jt;
    jt.resize(n+1,0);
    queue<int> q;
    q.push(jk);
    vector<bool> seen;
    seen.resize(n+1,0);
    seen[jk]=true;
    while (!q.empty()){
        int v=q.front();
        q.pop();
        for (int edge:g[v]){
            if (!seen[edge]){
                seen[edge]=true;
                jt[edge]=jt[v]+1;
                q.push(edge);
            }
        }
    }

    vector<int> tt;
    tt.resize(n+1,0);
    seen.clear();
    seen.resize(n+1,0);
    seen[tk]=true;
    q.push(tk);
    while (!q.empty()){
        int v=q.front();
        q.pop();
        for (int edge:g[v]){
            if (!seen[edge]){
                seen[edge]=true;
                tt[edge]=tt[v]+1;
                q.push(edge);
            }
        }
    }
    int ans=0;
    for (int i=1; i<=n;i++){
        if (jt[i]<tt[i]-1){
            ans=max(ans,tt[i]-1);
        }
    }
    cout<<(ans<k? "IGEN":"NEM")<<"\n";
}
int main()
{
    int t;
    cin>>t;
    while (t--) solve();
}