#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define pb push_back
#define fst first
#define snd second
template <typename t>
using vv = vector<t>;
template <typename a, typename b>
using pp = pair<a, b>;
typedef long long ll;
typedef double db;
const int mod = 1e9 + 7;
vv<pp<ll, ll>> st;
vv<int> lv;
int s = 1;
void push(int node) {
int u = node << 1;
lv[u] += lv[node];
st[u].fst += lv[node];
st[u].snd += lv[node];
lv[++u] += lv[node];
st[u].fst += lv[node];
st[u].snd += lv[node];
lv[node] = 0;
}
void upd(int x, int y, int l, int r, int node, int v) {
if (x > r || y < l) return;
if (x <= l && y >= r) {
st[node].fst += v;
st[node].snd += v;
lv[node] += v;
return;
}
int m = (l + r) / 2;
push(node);
upd(x, y, l, m, node * 2, v);
upd(x, y, m + 1, r, node * 2 + 1, v);
st[node].fst = st[node * 2 + 1].fst;
st[node].snd = st[node * 2].snd;
}
int cat(int l, int r, int node, int v) {
if (l == r) return l;
int m = (l + r) / 2;
push(node);
if (st[node * 2].fst <= v) return cat(l, m, node * 2, v);
return cat(m + 1, r, node * 2 + 1, v);
}
int dog(int l, int r, int node, int v) {
if (l == r) return l;
int m = (l + r) / 2;
push(node);
if (st[node * 2 + 1].snd >= v) return dog(m + 1, r, node * 2 + 1, v);
return dog(l, m, node * 2, v);
}
void get(int node) {
if (!node) return;
get(node >> 1);
if (node < s) push(node);
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int n;
cin >> n;
vv<pp<int, int>> idk(n);
for (auto& p : idk) cin >> p.fst >> p.snd;
sort(all(idk));
while (s < idk.back().fst) s <<= 1;
st.assign(s << 1, {0, 0});
lv.assign(s << 1, 0);
for (auto [h, k] : idk) {
int p = h - k;
get(p + s);
int x = st[p + s].fst;
int l = cat(0, s - 1, 1, x), r = dog(0, s - 1, 1, x);
r = min(r, h - 1);
int cnt = r - p + 1;
if (cnt) upd(l, l + cnt - 1, 0, s - 1, 1, 1);
if (r + 1 <= h - 1) upd(r + 1, h - 1, 0, s - 1, 1, 1);
}
for (int i = 1; i < s; i++) push(i);
ll ans = 0;
for (int i = s; i < s + idk.back().fst; i++) ans += st[i].fst * (st[i].fst - 1) / 2;
cout << ans;
return 0;
}
