#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int NMAX = 1e5 + 10;
ll answer;
int n;
pair<int, int> a[NMAX + 1];
struct AIB {
int n;
int aib[NMAX + 1];
void init(int n) {
this->n = n;
fill(aib + 1, aib + n + 1, 0);
}
void update(int pos, int value) {
for(int i = pos; i <= n; i += i & (-i)) {
aib[i] += value;
}
}
void update(int l, int r, int value) {
update(l, value);
update(r + 1, -value);
}
int query(int pos) {
int answer = 0;
for(int i = pos; i >= 1; i -= i & (-i)) {
answer += aib[i];
}
return answer;
}
}aib;
int last_greater(int ending, int value) {
int left = 1, right = ending, answer = 0;
while(left <= right) {
int mid = (left + right) / 2;
if(aib.query(mid) >= value) {
answer = mid;
left = mid + 1;
}
else {
right = mid - 1;
}
}
return answer;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n;
for(int i = 1; i <= n; i++) {
cin >> a[i].first >> a[i].second;
}
// cout << '\n';
int max_h = 0;
for(int i = 1; i <= n; i++) {
max_h = max(max_h, a[i].first);
}
aib.init(max_h);
sort(a + 1, a + n + 1);
for(int i = 1; i <= n; i++) {
auto [h, k] = a[i];
// for(int j = 1; j <= max_h; j++) {
// cout << aib.query(j) << ' ';
// }
// cout << '\n';
// cout << h << ' ' << k << '\n';
int l = h - k + 1;
int last = aib.query(l);
int last_pos_last = last_greater(h, last);
int first_pos_last = last_greater(h, last + 1) + 1;
int adding_right = h - last_pos_last;
int adding_left = k - adding_right;
// cout << last_pos_last + 1 << ' ' << h << '\n';
// cout << first_pos_last << ' ' << first_pos_last + adding_left - 1 << '\n';
aib.update(last_pos_last + 1, h, 1);
aib.update(first_pos_last, first_pos_last + adding_left - 1, 1);
}
for(int i = 1; i <= max_h; i++) {
int x = aib.query(i);
// cout << x << ' ';
answer += (ll) x * (x - 1) / 2;
}
cout << answer << '\n';
return 0;
}
