#include<cstdio>
#include<cmath>
#include<cstring>
#include<cctype>
#include<iostream>
#include<algorithm>
using namespace std;
const int N=8e4+10;
inline int read(){int X=0,w=0;char ch=0;while(!isdigit(ch)){w|=ch=='-';ch=getchar();}while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();return w?-X:X;
}
struct tree{int l,r,sum;
}tr[N*500];
struct node{int to,nxt;
}edge[N*2];
int a[N],b[N],rt[N],pool,n,m;
int dep[N],anc[N][20],son[N];
int cnt,head[N],fa[N],vis[N],tot;
inline void add(int u,int v){edge[++cnt].to=v;edge[cnt].nxt=head[u];head[u]=cnt;
}
inline void insert(int y,int &x,int l,int r,int p){tr[x=++pool]=tr[y];tr[x].sum++;if(l==r)return;int mid=(l+r)>>1;if(p<=mid)insert(tr[y].l,tr[x].l,l,mid,p);else insert(tr[y].r,tr[x].r,mid+1,r,p);
}
inline int query(int nl,int nr,int nm,int nfm,int l,int r,int k){if(l==r)return l;int delta=tr[tr[nl].l].sum+tr[tr[nr].l].sum-tr[tr[nm].l].sum-tr[tr[nfm].l].sum;int mid=(l+r)>>1;if(delta>=k)return query(tr[nl].l,tr[nr].l,tr[nm].l,tr[nfm].l,l,mid,k);else return query(tr[nl].r,tr[nr].r,tr[nm].r,tr[nfm].r,mid+1,r,k-delta);
}
inline void LSH(){sort(b+1,b+m+1);m=unique(b+1,b+m+1)-b-1;for(int i=1;i<=n;i++){a[i]=lower_bound(b+1,b+m+1,a[i])-b;}return;
}
inline int LCA(int i,int j){if(dep[i]<dep[j])swap(i,j);for(int k=16;k>=0;k--){if(dep[anc[i][k]]>=dep[j])i=anc[i][k];}if(i==j)return i;for(int k=16;k>=0;k--){if(anc[i][k]!=anc[j][k])i=anc[i][k],j=anc[j][k];}return anc[i][0];
}
int find(int x){if(fa[x]==x)return x;return fa[x]=find(fa[x]);
}
void dfs(int u,int f,int root){anc[u][0]=f;for(int k=1;k<=16;k++)anc[u][k]=anc[anc[u][k-1]][k-1];son[root]++;dep[u]=dep[f]+1;fa[u]=root;vis[u]=1;insert(rt[f],rt[u],1,m,a[u]);for(int i=head[u];i;i=edge[i].nxt){int v=edge[i].to;if(v!=f)dfs(v,u,root);}return;
}
int main(){read();n=read();int e=read(),T=read(),last=0;for(int i=1;i<=n;i++)a[i]=b[++m]=read(),fa[i]=i;LSH();for(int i=1;i<=e;i++){int x=read(),y=read();add(x,y);add(y,x);}for(int i=1;i<=n;i++)if(!vis[i]){dfs(i,0,++tot);fa[tot]=tot;}for(int i=1;i<=T;i++){char ch=getchar();while(ch!='Q'&&ch!='L')ch=getchar();if(ch=='Q'){int x=read()^last,y=read()^last,k=read()^last;int t=LCA(x,y),ft=anc[t][0];printf("%d\n",last=b[query(rt[x],rt[y],rt[t],rt[ft],1,m,k)]);}else{int x=read()^last,y=read()^last;add(x,y);add(y,x);int u=find(x),v=find(y);if(son[u]<son[v]){swap(u,v);swap(x,y);}dfs(y,x,u);}}return 0;
}