#include <bits/stdc++.h>
/*
Wake up, I'm wake up
Thu sang roi, em thay khong?
*/
using namespace std;
using ll = long long;
#define int long long
#define pii pair<ll, ll>
#define fi first
#define se second
const ll N = 2e5 + 5, inf = 1e18, mod = 1e9 + 7, block = 320, lim = 19;
int n;
pii a[N];
struct ST {
vector <int> st, lz, st1;
ST (int _n) {
st.assign(4 * (_n + 1), 0);
st1.assign(4 * (_n + 1), 0);
lz.assign(4 * (_n + 1), 0);
}
void lazy(int i, int l, int r) {
if (lz[i] != 0) {
if (l < r) {
st[2 * i] += lz[i];
st[2 * i + 1] += lz[i];
st1[2 * i] += lz[i];
st1[2 * i + 1] += lz[i];
lz[2 * i] += lz[i];
lz[2 * i + 1] += lz[i];
}
lz[i] = 0;
}
}
void update(int i, int l, int r, int u, int v, int val) {
if (u > r || v < l) return;
if (u <= l && r <= v) {
st[i] += val;
lz[i] += val;
st1[i] += val;
return;
}
lazy(i, l, r);
int mid = (l + r) / 2;
update(2 * i, l, mid, u, v, val);
update(2 * i + 1, mid + 1, r, u, v, val);
st[i] = min(st[2 * i], st[2 * i + 1]);
st1[i] = max(st1[2 * i], st1[2 * i + 1]);
}
int get(int i, int l, int r, int u, int v) {
lazy(i, l, r);
if (u > r || v < l) return inf;
if (u <= l && r <= v) return st[i];
int mid = (l + r) / 2;
return min(get(2 * i, l, mid, u, v), get(2 * i + 1, mid + 1, r, u, v));
}
int findR(int i, int l, int r, int u, int v, int val) {
if (u > r || v < l) return -1;
lazy(i, l, r);
if (st[i] > val) return -1;
if (l == r) return l;
int mid = (l + r) / 2;
int ans = -1;
if (!(v < mid + 1 || u > r)) {
if (st[2 * i + 1] <= val) ans = findR(2 * i + 1, mid + 1, r, u, v, val);
}
if (ans == -1) {
if (!(v < l || u > mid)) {
if (st[2 * i] <= val) ans = findR(2 * i, l, mid, u, v, val);
}
}
return ans;
}
int findL(int i, int l, int r, int u, int v, int val) {
if (u > r || v < l) return -1;
lazy(i, l, r);
if (st1[i] <= val) return -1;
if (l == r) return l;
int mid = (l + r) / 2;
int ans = -1;
if (!(v < mid + 1 || u > r)) {
if (st1[2 * i + 1] > val) ans = findL(2 * i + 1, mid + 1, r, u, v, val);
}
if (ans == -1) {
if (!(v < l || u > mid)) {
if (st1[2 * i] > val) ans = findL(2 * i, l, mid, u, v, val);
}
}
return ans;
}
} st(N);
vector<int> bit;
int maxx = 0;
void update(int idx, int v) {
while (idx <= maxx) {
bit[idx] += v;
idx += idx & -idx;
}
}
int get(int idx) {
if (idx <= 0) return 0;
int ans = 0;
while (idx > 0) {
ans += bit[idx];
idx -= idx & -idx;
}
return ans;
}
int find(int u, int gh) {
if (u < 0) return gh + 1;
int l = 1, r = gh, ans = gh + 1;
while (l <= r) {
int mid = (l + r) / 2;
if (get(mid) <= u) {
ans = mid;
r = mid - 1;
} else l = mid + 1;
}
return ans;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
if (fopen(".inp", "r")) {
freopen(".inp", "r", stdin);
freopen(".out", "w", stdout);
}
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i].fi >> a[i].se;
maxx = max(maxx, a[i].fi);
}
sort(a + 1, a + n + 1);
bit.assign(maxx + 5, 0);
for (int i = 1; i <= n; i++) {
int l = a[i].fi;
int r = l - a[i].se + 1;
int u = (r >= 1 ? get(r) : -1);
int kt = find(u, l);
int bd = find(u - 1, l) - 1;
int len = bd - r + 1;
if (bd + 1 <= l) {
update(bd + 1, 1);
update(l + 1, -1);
}
if (len > 0) {
update(kt, 1);
update(kt + len, -1);
}
}
int ans = 0;
for (int i = 1; i <= maxx; i++) {
int val = get(i);
ans += val * (val - 1) / 2;
}
cout << ans << '\n';
return 0;
}
