#include <bits/stdc++.h>
#define L long long
using namespace std;
const int H = (int)1e5;
struct FenwickTree {
int N;
vector<int> fw;
void update(int x, int v) {
while (x <= N) fw[x] += v, x += x & -x;
}
void range_update(int l, int r, int v) {
if (l > r) return;
update(l, v);
update(r+1, -v);
}
int query(int x) {
int res = 0;
while (x > 0) res += fw[x], x -= x & -x;
return res;
}
int low(int x, int l, int r) {
r++;
while (l < r) {
int mid = (l + r) / 2;
if (query(mid) <= x) r = mid;
else l = mid + 1;
}
return l;
}
int high(int x, int l, int r) {
l--;
while (l < r) {
int mid = (l + r + 1) / 2;
if (query(mid) >= x) l = mid;
else r = mid - 1;
}
return l;
}
} T;
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n; cin >> n;
T.N = H, T.fw.assign(H+1, 0);
vector<pair<int, int>> a(n+1);
for (int i = 1; i <= n; i++) cin >> a[i].first >> a[i].second;
sort(a.begin() + 1, a.end());
for (int i = 1; i <= n; i++) {
int x = T.query(a[i].first - a[i].second + 1);
int l = T.high(x, 1, a[i].first) + 1, r = a[i].first;
T.range_update(l, r, 1);
int ll = T.low(x, 1, a[i].first);
int rr = ll + a[i].second - r + l - 2;
T.range_update(ll, rr, 1);
}
L ans = 0;
for (int i = 1; i <= H; i++) ans += (L)T.query(i) * (L)(T.query(i) - 1) / 2;
cout << ans;
}
