#include<bits/stdc++.h>

using namespace std;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

using ll = long long;

#define int long long

struct fenwick {
    int n;
    vector<int> fenw;

    fenwick() = default;
    fenwick(int n) : n(n) {
        fenw.assign(n, 0);
    }

    void upd(int k, int x) {
        for (; k < n; k = (k | (k + 1))) {
            fenw[k] += x;
        }
    }

    int get(int k) {
        int res = 0;
        for (; k >= 0; k = (k & (k + 1)) - 1) {
            res += fenw[k];
        }
        return res;
    }

    int get(int l, int r) {
        return get(r) - get(l - 1);
    }
};

void solve() {
    int n, k, m, q;
    cin >> n >> k >> m >> q;
    --k;
    vector<int> c(n), x(m + 1);
    for (auto& i : c) cin >> i;
    for (auto& i : x) cin >> i;
    vector<bool> co(n, 0), xo(m + 1, 0);
    fenwick flenc(n), flenx(m + 1), foc(n), fox(m + 1);
    for (int i = 0; i < n; ++i) {
        flenc.upd(i, c[i]);
    }
    for (int i = 0; i <= m; ++i) {
        flenx.upd(i, x[i]);
    }
    auto checkc = [&](int u, int v) -> bool {
        if (u <= v) return foc.get(u, v - 1) == 0;
        return foc.get(0, n - 1) - foc.get(v, u - 1) == 0;
    };
    auto checkx = [&](int u, int v) -> bool {
        if (u > v) swap(u, v);
        return fox.get(u, v - 1) == 0;
    };
    auto distc = [&](int u, int v) -> int {
        if (!checkc(u, v)) return 1e15;
        if (u <= v) return flenc.get(u, v - 1);
        return flenc.get(0, n - 1) - flenc.get(v, u - 1);
    };
    auto distx = [&](int u, int v) -> int {
        if (u > v) swap(u, v);
        if (!checkx(u, v)) return 1e15;
        return flenx.get(u, v - 1);
    };
    auto dist0 = [&](int u) -> int {
        if (u >= n) return distx(0, u - n + 1);
        return min(distc(0, u), distc(u, 0));
    };
    auto distk = [&](int u) -> int {
        if (u >= n) return distx(m, u - n + 1);
        return min(distc(k, u), distc(u, k));
    };
    while (q--) {
        char qq;
        cin >> qq;
        if (qq == 'c') {
            int k;
            cin >> k;
            --k;
            if (!co[k]) {
                co[k] = 1;
                foc.upd(k, 1);
            } else {
                co[k] = 0;
                foc.upd(k, -1);
            }
        } else if (qq == 'x') {
            int k;
            cin >> k;
            if (!xo[k]) {
                xo[k] = 1;
                fox.upd(k, 1);
            } else {
                xo[k] = 0;
                fox.upd(k, -1);
            }
        } else {
            int u, v;
            cin >> u >> v;
            --u, --v;
            int ans = 1e15;
            ans = min(ans, dist0(u) + dist0(v));
            ans = min(ans, distk(u) + distk(v));
            ans = min(ans, dist0(u) + distx(0, m + 1) + distk(v));
            ans = min(ans, dist0(v) + distx(0, m + 1) + distk(u));
            if (max(u, v) < n) {
                ans = min(ans, distc(u, v));
                ans = min(ans, distc(v, u));
            }
            if (min(u, v) >= n) {
                ans = min(ans, distx(u - n + 1, v - n + 1));
            }
            if (ans == 1e15) cout << "impossible\n";
            else cout << ans << '\n';
        }
    }
}

int32_t main() {
#ifndef LOCAL
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#else
    freopen("input.txt", "r", stdin);
#endif
    int t = 1;
//    cin >> t;
    while (t--)
        solve();
    return 0;
}