#include <bits/stdc++.h>

using namespace std;
const int INF=1e9;
#define N 2000006
int seg[N*4], arr[N];
int n, k, m, q, segn;
void build(int ind, int l, int r){
  if(l==r){
    seg[ind] = arr[l];
    return;
  }
  int mid = (l+r)>>1;
  build(ind*2, l, mid);
  build(ind*2+1, mid+1, r);
  seg[ind] = seg[ind*2]+seg[ind*2+1];
}
int query(int ind, int l, int r, int ql, int qr){
  if(r<ql || qr<l || r<l){
    return 0;
  }
  if(ql<=l && r<=qr){
    return seg[ind];
  }
  int mid = (l+r)>>1;
  return min(query(ind*2, l, mid, ql, qr)+query(ind*2+1, mid+1, r, ql, qr), INF);
}
void modify(int ind, int l, int r, int pos){
  if(l==r){
    if(seg[ind]==INF){
      seg[ind] = arr[l];
    }
    else{
      seg[ind] = INF;
    }
    return;
  }
  int mid = (l+r)>>1;
  if(pos<=mid)
    modify(ind*2, l, mid, pos);
  else{
    modify(ind*2+1, mid+1, r, pos);    
  }
  seg[ind] = min(seg[ind*2]+seg[ind*2+1], INF);
}
void solve() {
  cin >> n >> k >> m >> q;
  segn = n+m+1;
  for(int i=1; i<=n; ++i){
    cin >> arr[i];
  }
  for(int i=n+1; i<=n+1+m; ++i){
    cin >> arr[i];
  }
  build(1, 1, segn);
  while(q--){
    char typ; cin >> typ;
    if(typ=='q'){
      int a, b; cin >> a >> b;
      if(b<a){
        swap(a, b);
      }
      if(a==b){
        cout << "0\n";
      }
      else{
        //a<b
        int tmpans;
        if(a>k && b<=n){ // 1
          tmpans = min(query(1, 1, segn, a, b-1), min(query(1, 1, segn, 1, a-1)+query(1, 1, segn, b, n), query(1, 1, segn, b, n+m+1)+query(1, 1, segn, k, a-1)));
        }
        else if(b<k){ // 2
          tmpans = min(query(1, 1, segn, a, b-1), min(query(1, 1, segn, 1, a-1)+query(1, 1, segn, b, n), query(1, 1, segn, b, k-1)+query(1, 1, segn, 1, a-1)+query(1, 1, segn, n+1, n+m+1)));
        }
        else if(a<k && (k<b && b<=n)){ // 3
          int ans1 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, b, n);
          int ans2 = query(1, 1, segn, a, b-1);
          int ans3 = query(1, 1, segn, a, k-1)+query(1, 1, segn, b, n+1+m);
          int ans4 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, n+1, n+m+1)+query(1, 1, segn, k, b-1);
          tmpans = min(ans1, min(ans2, min(ans3, ans4)));
        }
        else if(a==1 && b==k){ // 4
          int ans1 = query(1, 1, segn, 1, k-1);
          int ans2 = query(1, 1, segn, k, n);
          int ans3 = query(1, 1, segn, n+1, n+1+m);
          tmpans = min(ans1, min(ans2, ans3));
        }
        else if(a==1 && b<k){ // 5
          int ans1 = query(1, 1, segn, a, b-1);
          int ans2 = query(1, 1, segn, b, n);
          int ans3 = query(1, 1, segn, b, k-1)+query(1, 1, segn, n+1 ,n+m+1);
          tmpans = min(ans1, min(ans2, ans3));
        }
        else if(a==1 && (k<b && b<=n)){ // 6
          int ans1 = query(1, 1, segn, b, n);
          int ans2 = query(1, 1, segn, a, b-1);
          int ans3 = query(1, 1, segn, k, b-1)+query(1, 1, segn, n+1, n+1+m);
          tmpans = min(ans1, min(ans2, ans3));
        }
        else if(a<k && b==k){
          int ans1 = query(1, 1, segn, a, b-1);
          int ans2 = query(1,1 , segn, 1, a-1)+query(1, 1, segn, b, n);
          int ans3 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, n+1, n+1+m);
          tmpans = min(ans1, min(ans2, ans3));
        }
        else if(a==k && b<=n){ // 8
          int ans1 = query(1, 1, segn, a, b-1);
          int ans2 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, b, n);
          int ans3 = query(1, 1, segn, b, n)+query(1, 1, segn, n+1, n+m+1);
          tmpans = min(ans1, min(ans2, ans3));
        }
        else if((k<a && a<=n) && n<b){ // 9
          int ans1 = query(1, 1, segn, a, n)+query(1, 1, segn, n+1, b);
          int ans2 = query(1, 1, segn, k, a-1)+query(1, 1, segn, b, n+1+m);
          int ans3 = query(1, 1, segn, 1, k-1)+query(1, 1, segn, a, n)+query(1, 1, segn, b, n+1+m);
          int ans4 = query(1, 1, segn, 1, a)+query(1, 1, segn, n+1, b-1);
          tmpans = min(ans1, min(ans2, min(ans3, ans4)));
        }
        else if(a<k && n<b){
          int ans1 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, n+1, b);
          int ans2 = query(1, 1, segn, a, k-1)+query(1, 1, segn, b, n+1+m);
          int ans3 = query(1, 1, segn, 1, a-1)+query(1, 1, segn, k, n)+query(1, 1, segn, b, n+1+m);
          int ans4 = query(1, 1, segn, a, b);
          tmpans = min({ans1, ans2, ans3, ans4});
        }
        else if(a==1 && n<b){
          int ans1 = query(1, 1, segn, n+1, b);
          int ans2 = query(1, 1, segn, k, n)+query(1, 1, segn, b, n+1+m);
          int ans3 = query(1, 1, segn, 1, k-1)+query(1, 1, segn, b, n+m+1);
          tmpans = min({ans1, ans2, ans3});
        }
        else if(a==k && n<b){// 12
          int ans1 = query(1, 1, segn, b, n+1+m);
          int ans2 = query(1, 1, segn, n+1, b)+query(1, 1, segn, 1, k-1);
          int ans3 = query(1, 1, segn, n+1, b)+query(1, 1, segn, k ,n);
          tmpans = min({ans1, ans2, ans3});
        }
        else if(n<a){
          int ans1 = query(1, 1, segn, a, b);
          int ans2 = query(1, 1, segn, 1, k-1)+query(1, 1, segn, n+1, a)+query(1, 1, segn, b, n+1+m);
          int ans3 = query(1, 1, segn, k, a)+query(1, 1, segn, b, n+1+m);
          tmpans = min({ans1, ans2, ans3});
        }
        else {
          assert(false);
        }
        if(tmpans>=INF){
          cout << "impossible\n";
        }
        else{
          cout << tmpans << '\n';
        }
      }
    }
    else if(typ=='x'){
      int tmp; cin >> tmp; tmp+=n+1;
      modify(1, 1, segn, tmp);
    }
    else{// c
      int tmp; cin >> tmp;
      modify(1, 1, segn, tmp);
    }
  }
}

signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int T = 1;
  // cin >> T;
  while (T--) solve();
}