#include <bits/stdc++.h>
// mrrrowwww meeowwwww :3
// go play vivid/stasis! !! !!! https://vividstasis.gay
#define fo(i, a, b) for (auto i = (a); i < (b); i++)
#define of(i, a, b) for (auto i = (b); i-- > (a);)
#define f first
#define s second
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define be(a) a.begin(), a.end()
using namespace std;
int ____init = []{
ios::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
return 0;
}();
int a[100001];
int bit[100002];
int get(int i) {
int res = 0;
for (i++; i > 0; i -= i & -i) res += bit[i];
return res;
}
void add(int i, int v) {
a[i] += v;
for (i++; i <= 100000; i += i & -i) bit[i] += v;
}
int main() {
int n; cin >> n;
vector<pair<int, int>> v(n);
int max_h = 0;
fo(i, 0, n) cin >> v[i].f >> v[i].s, max_h = max(max_h, v[i].f);
sort(be(v));
for (auto [h, k] : v) {
add(h, -1);
if (a[h - k]) {
add(h - k, 1);
} else {
int start_hk = get(h - k);
int l = 0, r = h - k;
while (l < r) {
int mid = (l + r) / 2;
if (get(mid) != start_hk) l = mid + 1;
else r = mid;
}
int hk_left = l;
l = h - k, r = h;
while (l < r) {
int mid = (l + r) / 2;
if (get(mid) != start_hk) r = mid;
else l = mid + 1;
}
int hk_right = l;
add(hk_left, 1);
add(hk_left + hk_right - (h - k), -1);
add(hk_right, 1);
}
}
long long res = 0;
int acc = 0;
fo(i, 0, max_h) acc += a[i], res += (long long) acc * (acc - 1) / 2;
cout << res;
}
