#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
const int NUM_ROWS = 1e5;
vector<int> aib(NUM_ROWS + 1);
vector<int> row_ids(NUM_ROWS + 1);
vector<pair<int, int>> rows;
int query (int k) {
int ans = 0;
while (k >= 1) {
ans += aib[k];
k -= (k & (-k));
}
return ans;
}
void update (int k, int val) {
while (k <= NUM_ROWS) {
aib[k] += val;
k += (k & (-k));
}
}
void range_update (int l, int r, int val) {
update(l, +val);
update(r + 1, -val);
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, i, h, k, delta, num_delta, lb_pos, ub_pos, ans;
cin >> n;
for (i = 0; i <= NUM_ROWS; i++) {
row_ids[i] = i;
}
rows = vector<pair<int, int>>(n + 1);
for (i = 1; i <= n; i++) {
cin >> rows[i].first >> rows[i].second;
}
sort(rows.begin() + 1, rows.end());
for (i = 1; i <= n; i++) {
h = rows[i].first;
k = rows[i].second;
delta = h - k + 1;
num_delta = query(delta);
auto it_lb =
lower_bound(row_ids.begin() + 1, row_ids.begin() + h + 1, num_delta,
[] (int mij, int val) { return query(mij) > val; });
lb_pos = it_lb - row_ids.begin();
auto it_ub =
upper_bound(row_ids.begin() + 1, row_ids.begin() + h + 1, num_delta,
[] (int val, int mij) { return query(mij) < val; });
ub_pos = it_ub - 1 - row_ids.begin();
range_update(lb_pos, lb_pos + ub_pos - delta, 1);
range_update(ub_pos + 1, h, 1);
}
ans = 0;
for (i = 1; i <= NUM_ROWS; i++) {
num_delta = query(i);
ans += num_delta * (num_delta - 1) / 2;
}
cout << ans << "\n";
return 0;
}
