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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define f first
#define s second
using namespace std;
using namespace __gnu_pbds;
using ii = pair<int, int>;
template<typename T> using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
constexpr int MAXN = 100001;
vector<int> T[MAXN + 1];
ordered_set<int> S[4 * MAXN + 4];
void build(int l = 0, int r = MAXN, int n = 1) {
if (l == r) {
for (auto& y : T[l]) S[n].insert(y);
}
else {
int m = (l + r) >> 1;
build(l, m, n << 1), build(m + 1, r, n << 1 | 1);
for (auto& y : S[n << 1]) S[n].insert(y);
for (auto& y : S[n << 1 | 1]) S[n].insert(y);
}
}
int query(int xl, int xr, int yl, int yr, int l = 0, int r = MAXN, int n = 1) {
if (l > r || l > xr || r < xl) return 0;
if (l >= xl && r <= xr) return S[n].order_of_key(yr + 1) - S[n].order_of_key(yl);
else {
int m = (l + r) >> 1;
return query(xl, xr, yl, yr, l, m, n << 1) + query(xl, xr, yl, yr, m + 1, r, n << 1 | 1);
}
}
ii P[100001];
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int N; cin >> N;
for (int i = 0; i < N; ++i) cin >> P[i].f >> P[i].s;
vector<ii> tmp;
for (int i = 0; i < N; ++i) tmp.emplace_back(P[i].f, i);
sort(begin(tmp), end(tmp));
for (int i = 0; i < N; ++i) {
if (i && tmp[i].f == tmp[i - 1].f) P[tmp[i].s].f = P[tmp[i - 1].s].f;
else P[tmp[i].s].f = i;
}
tmp.clear();
for (int i = 0; i < N; ++i) tmp.emplace_back(P[i].s, i);
sort(begin(tmp), end(tmp));
for (int i = 0; i < N; ++i) {
if (i && tmp[i].f == tmp[i - 1].f) P[tmp[i].s].s = P[tmp[i - 1].s].s;
else P[tmp[i].s].s = i;
}
for (int i = 0; i < N; ++i) T[P[i].f].push_back(P[i].s);
build();
vector<ii> X, Y;
for (int i = 0; i < N; ++i) X.push_back(P[i]), Y.push_back(P[i]);
auto cmpy = [](const ii & a, const ii & b) { return a.s < b.s || (a.s == b.s && a.f < b.f); };
sort(begin(X), end(X));
sort(begin(Y), end(Y), cmpy);
unique(begin(X), end(X));
unique(begin(Y), end(Y), cmpy);
int ans = 0;
for (int i = 0; i < N; ++i) {
auto it = lower_bound(begin(X), end(X), ii(P[i].f, P[i].s));
int yh = (next(it) != end(X) && next(it)->f == P[i].f ? next(it)->s : MAXN + 1);
int yl = (it != begin(X) && prev(it)->f == P[i].f ? prev(it)->s : -2);
it = lower_bound(begin(Y), end(Y), ii(P[i].f, P[i].s), cmpy);
int xh = (next(it) != end(Y) && next(it)->s == P[i].s ? next(it)->f : MAXN + 1);
int xl = (it != begin(Y) && prev(it)->s == P[i].s ? prev(it)->f : -2);
int q = query(xl + 1, xh - 1, yl + 1, yh - 1);
if (q > 1) ++ans;
}
cout << ans << '\n';
}
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