1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
#include <bits/stdc++.h>
#define st first 
#define nd second 
using namespace std;

set<pair<int, int>> blocks, cp;


bool removable(int a, int b) {
    if (cp.find({a, b}) == cp.end()) return false;
    if (cp.find({a, b+1}) == cp.end() && cp.find({a, b-1}) == cp.end()) return true;
    if (cp.find({a+1, b}) == cp.end() && cp.find({a-1, b}) == cp.end()) return true;
    return false;
}

vector<pair<int, int>> v = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

void solve() {
    vector<pair<int, int>> to_rem;
    cp = blocks;
    for (auto p: cp) {
        if (removable(p.st, p.nd)) to_rem.push_back(p);
    }
    int ans = 0;
    while (!to_rem.empty()) {
        pair<int, int> p = to_rem.back();
        to_rem.pop_back();
        if (cp.find(p) == cp.end()) continue;
        cp.erase(p);
        ans++;
        for (pair<int, int> d: v) {
            if (removable(p.st+d.st, p.nd+d.nd)) to_rem.push_back({p.st+d.st, p.nd+d.nd});
        }
    }
    cout << ans << '\n';
    return;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, m, k, q;
    cin >> n >> m >> k >> q;


    for (int i = 0; i < k; i++) {
        int x, y; cin >> x >> y;
        blocks.insert({x, y});
    }
    solve();
    for (int i = 0; i < q; i++) {
        int a, b; cin >> a >> b;
        if (blocks.find({a, b}) != blocks.end()) {
            blocks.erase({a, b});
        }
        else blocks.insert({a, b});
        solve();
    }

}