#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll
#define all(v) v.begin(),v.end()
#define pb push_back

void dbg_out() {cerr << endl; }
template< typename H, typename... T> 
void dbg_out(H h, T... t) { cerr << ' ' << h; dbg_out(t...); }
#define dbg(...) { cerr << #__VA_ARGS__ << ':'; dbg_out(__VA_ARGS__); }

const int N = 2e6 + 10;

int n, k, m, q, c[N], x[N];

void solve () {
	// u, 1, k, v
	// u, k, 1, v
	// u, v
	// u, 1, v
	// u, k, v	
	cin >> n >> k >> m >> q;
	for (int i = 1; i <= n; i++) cin >> c[i];
	for (int i = 0; i <= m; i++) cin >> x[i];

	int L = 0, M = 0, R = 0;
	vector dist (2, vector<int> (n + m + 1));
	{
		int cur = 0;
		for (int i = 1; i < k; i++) {
			cur += c[i];
			dist[0][i + 1] = cur;
		}
		R = cur;
	}
	{
		int cur = 0;
		for (int i = 0; i < m; i++) {
			cur += x[i];
			dist[0][n + i + 1] = cur;
		}
		M = cur + x[m];
	}
	{
		int cur = 0;
		for (int i = n; i >= k; i--) {
			cur += c[i];
			dist[0][i] = cur;
		}
		L = cur;
	}

	// vamos calcular agora a distancia para k
	{
		int cur = 0;
		for (int i = k - 1; i >= 1; i--) {
			cur += c[i];
			dist[1][i] = cur;
		}
	}
	{
		int cur = 0;
		for (int i = k + 1; i <= n; i++) {
			cur += c[i - 1];
			dist[1][i] = cur;
		}
	}
	{
		int cur = 0;
		for (int i = n + m; i >= n + 1; i--) {
			cur += x[i - n];
			dist[1][i] = cur;
		}
	}

	// dbg (L, M, R);
	// for (int i = 1; i <= n + m; i++) cout << dist[0][i] << " ";
	// cout << "\n";
	// for (int i = 1; i <= n + m; i++) cout << dist[1][i] << " ";
	// cout << "\n";

	set<int> esq, meio, dir;
	const int INF = 1e17;

	while (q--) {
		char op; cin >> op;

		if (op == 'x') {
			int j; cin >> j;
			if (meio.find (j) != meio.end ()) meio.erase (j);
			else meio.insert (j);
		}
		else if (op == 'c') {
			int j; cin >> j;
			if (j < k) {
				if (dir.find (j) != dir.end ()) dir.erase (j);
				else dir.insert (j);
			}
			else {
				if (esq.find (j) != esq.end ()) esq.erase (j);
				else esq.insert (j);
			}
		}
		else {

			auto find_path = [&] (int u, int pivot) -> bool {
				// vamos tentar ir do u para pivot
				if (u == pivot) return 1;
				if (pivot == 1) {
					if (u == k) return !esq.size () || !dir.size () || !meio.size ();

					if (u < k) return !dir.size () || *dir.begin () >= u;
					else if (u <= n) return !esq.size () || *--esq.end () < u;
					else return !meio.size () || *meio.begin () >= u - n;
				}
				else {
					assert (pivot == k);
					if (u == 1) return !esq.size () || !dir.size () || !meio.size ();

					if (u < k) return !dir.size () || *--dir.end () < u;
					else if (u <= n) return !esq.size () || *esq.begin () >= u;
					else return !meio.size () || *--meio.end () < u - n;
				}
			};
			
			int u, v; cin >> u >> v;
			if (u > v) swap (u, v);
			int ans = INF;

			// vamos tentar ir direto
			if (1 <= u && v < k) {
				// se estao na direita!
				auto it = dir.lower_bound (u);
				if (it == dir.end () || *it >= v) ans = min (ans, dist[0][v] - dist[0][u]);
			}
			if (k <= u && v <= n) {
				// se estao na esquerda!
				auto it = esq.lower_bound (u);
				if (it == esq.end () || *it >= v) ans = min (ans, dist[1][v] - dist[1][u]);
			}
			if (n + 1 <= u && v <= n + m) {
				// se estao no meio
				auto it = meio.lower_bound (u - n);
				if (it == meio.end () || *it >= v) ans = min (ans, dist[0][v] - dist[0][u]);
			}

			if (u == 1 && v == k) {
				if (!esq.size ()) ans = min (ans, L);
				if (!dir.size ()) ans = min (ans, R);
				if (!meio.size ()) ans = min (ans, M);
			}
			else {
				// se consigo fazer u -> 1
				if (u != k) {
					int cur = 0;
					if (find_path (u, 1)) {
						cur += dist[0][u];
						// dbg (cur);
						// tentamos ir direto para v
						if (v != k && find_path (v, 1)) {
							ans = min (ans, cur + dist[0][v]);
							// dbg (cur +dist[0][v]);
						}
						// tentamos ir para k
						int bridge = INF;
						if (!esq.size ()) bridge = min (bridge, L);
						if (!dir.size ()) bridge = min (bridge, R);
						if (!meio.size ()) bridge = min (bridge, M);

						if (bridge != INF) {
							cur += bridge;
							// dbg (cur);
							if (find_path (v, k)) {
								ans = min (ans, cur + dist[1][v]);
							}
						}
					}  
				}
				if (u != 1) {
					int cur = 0;
					if (find_path (u, k)) {
						cur += dist[1][u];
						// tentamos ir direto para v
						if (find_path (v, k)) {
							assert (v != 1);
							ans = min (ans, cur + dist[1][v]);
						}
						// tentamos ir para k
						int bridge = INF;
						if (!esq.size ()) bridge = min (bridge, L);
						if (!dir.size ()) bridge = min (bridge, R);
						if (!meio.size ()) bridge = min (bridge, M);

						if (bridge != INF) {
							cur += bridge;
							if (find_path (v, 1)) {
								ans = min (ans, cur + dist[0][v]);
							}
						}
					}  
				}

			}

			if (ans == INF) cout << "impossible\n";
			else cout << ans << "\n";
		}
	}
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	solve();
}