//Huyduocdithitp
#include<bits/stdc++.h>
typedef int ll;
#define endl '\n'
#define fi first
#define se second
#define pii pair<ll,ll>
#define N 100005
#define LOG 18
using namespace std;
const ll inf = 1e9;
bool ghuy4g;
ll n, m;
pii a[N];
ll st[4 * N], f[4 * N];
void lazy(ll id) {
if (f[id] == 0) return;
st[id] += f[id];
if (id * 2 < 4 * N) {
f[id * 2] += f[id];
}
if (id * 2 + 1 < 4 * N) {
f[id * 2 + 1] += f[id];
}
f[id] = 0;
}
ll bit[N];
void upd(ll u, ll v) {
ll idx = u;
while (idx <= m) {
bit[idx] += v;
idx += idx & (-idx);
}
}
ll ge(ll u) {
ll idx = u, ans = 0;
while (idx > 0) {
ans += bit[idx];
idx -= idx & (-idx);
}
return ans;
}
void update(ll id, ll l, ll r, ll L, ll R, ll v) {
upd(L, 1);
upd(R + 1, -1);
return;
if (L > R) return;
lazy(id);
if (l > R || r < L) return;
if (L <= l && r <= R) {
f[id] += v;
lazy(id);
return;
}
ll mid = (l + r) / 2;
update(id * 2, l, mid, L, R, v);
update(id * 2 + 1, mid + 1, r, L, R, v);
st[id] = min(st[id * 2], st[id * 2 + 1]);
}
ll get(ll id, ll l, ll r, ll i) {
return ge(i);
lazy(id);
if (i > r || i < l) return inf;
if (l == r) {
return st[id];
}
ll mid = (l + r) / 2;
return min(get(id * 2, l, mid, i), get(id * 2 + 1, mid + 1, r, i));
}
ll find(ll u, ll gh) { // vi tri pos nho nhat ma a[pos] <= u
if (u < 0) return gh + 1;
ll l = 1, r = gh, ans = gh + 1;
while (l <= r) {
ll mid = (l + r) / 2;
if (get(1, 1, m, mid) <= u) {
ans = mid;
r = mid - 1;
}
else {
l = mid + 1;
}
}
return ans;
}
void solve() {
for (int i = 1; i <= n; i ++) {
//cout << "i " << a[i].fi << " " << a[i].se << endl;
ll l = a[i].fi, r = l - a[i].se + 1;
ll u = get(1, 1, m, r);
ll kt = find(u, a[i].fi), bd = find(u - 1, a[i].fi) - 1;
ll len = bd - r + 1;
//cout << " " << l << " " << r << " " << bd << " " << kt << " " << len << endl;
if (bd + 1 <= l) {
upd(bd + 1, 1);
upd(l + 1, -1);
//update(1, 1, m, bd + 1, l, 1);
//cout << " -" << "upd " << bd + 1 << " " << l << endl;
}
//update(1, 1, m, kt, kt + len - 1, 1);
upd(kt, 1);
upd(kt + len, -1);
//cout << " -" << "upd " << kt << " " << kt + len - 1 << endl;
/*for (int j = 1; j <= m; j ++) {
//cout << get(1, 1, m, j) << " ";
}*/
//cout << endl;
}
long long ans = 0;
for (int i = 1; i <= m; i ++) {
ll xet = get(1, 1, m, i);
ans += (long long)xet * (long long)(xet - 1) / 2;
}
cout << ans;
}
bool klinh;
signed main() {
//freopen("test.inp", "r", stdin);
//freopen("test.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i ++) {
cin >> a[i].fi >> a[i].se;
m = max(m, a[i].fi);
}
sort(a + 1, a + 1 + n);
solve();
cerr << fabs(&klinh - &ghuy4g) / double(1024 * 1024);
return 0;
}
