#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<int> st;
int m;
void add(int v, int l, int r, int tl, int tr) {
if (l > r) return;
if (tl == l && tr == r) {
st[v] ++; return;
}
int tm = (tl + tr) / 2;
add(v * 2, l, min(r, tm), tl, tm);
add(v * 2 + 1, max(l, tm + 1), r, tm + 1, tr);
return;
}
int get(int v, int tl, int tr, int pos) {
if (tl == tr) return st[v];
int tm = (tl + tr) / 2;
if (pos <= tm) return st[v] + get(v * 2, tl, tm, pos);
else return st[v] + get(v * 2 + 1, tm + 1, tr, pos);
}
bool binsearch(int mid, int x) {
int val = get(1, 0, m - 1, mid);
if (val >= x) return true;
else return false;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n; cin >> n;
vector<pair<int, int>> v(n);
for (int i = 0; i < n; i ++) cin >> v[i].first >> v[i].second;
sort(v.begin(), v.end());
m = v[n - 1].first;
vector<int> db(m);
st.resize(4 * m + 1);
for (int i = 0; i < n; i ++) {
int ind = v[i].first - v[i].second;
int x = get(1, 0, m - 1, ind);
int l = 0, r = v[i].first;
while (l < r - 1) {
int mid = (l + r) / 2;
if (binsearch(mid, x)) l = mid;
else r = mid;
}
add(1, r, v[i].first - 1, 0, m - 1);
int cnt = max(0, v[i].first - r);
l = -1, r = v[i].first - 1;
while (l < r - 1) {
int mid = (l + r) / 2;
if (binsearch(mid, x + 1)) l = mid;
else r = mid;
}
add(1, r, r + v[i].second - cnt - 1, 0, m - 1);
}
ll ans = 0;
for (int i = 0; i < m; i ++) {
ll c = ll(get(1, 0, m - 1, i));
ans += c * (c - 1) / 2;
}
cout << ans;
return 0;
}
