#include <bits/stdc++.h>
#define int long long
using namespace std;
struct sgt {
int n;
vector<int> seg, lazy;
void init(int sz) {
n = sz;
seg.assign(4*n+10, 0);
lazy.assign(4*n+10, 0);
}
void push(int l, int r, int node) {
if(lazy[node] == 0) return;
seg[node] += (r-l+1)*lazy[node];
if(l != r) {
lazy[node*2+1] += lazy[node];
lazy[node*2+2] += lazy[node];
}
lazy[node] = 0;
}
void update(int l, int r, int idl, int idr, int val, int node) {
push(l, r, node);
if(l > idr || r < idl) return;
if(idl <= l && r <= idr) {
lazy[node] += val;
push(l, r, node);
return;
}
int mid = (l+r)/2;
update(l, mid, idl, idr, val, node*2+1);
update(mid+1, r, idl ,idr, val, node*2+2);
seg[node] = seg[node*2+1] + seg[node*2+2];
}
int query(int l, int r, int ql, int qr, int node) {
push(l, r, node);
if(l > qr || r < ql) return 0;
if(l >= ql && r <= qr) return seg[node];
int mid = (l+r)/2;
return query(l, mid, ql, qr, node*2+1) + query(mid+1, r, ql, qr, node*2+2);
}
void upd(int idl, int idr, int val) {
update(0, n, idl, idr, val, 0);
}
int qry(int ql, int qr) {
return query(0, n, ql, qr, 0);
}
};
sgt seg;
int ubound(int val, int range) {
int l=1, r=range;
if(val > seg.qry(1, 1)) return -1;
while(l < r) {
int mid = (l+r+1)/2;
if(seg.qry(mid, mid) >= val) l = mid;
else r = mid-1;
}
return l;
}
int lbound(int val, int range) {
int l=1, r=range;
if(val < seg.qry(range, range)) return -1;
while(l < r) {
int mid = (l+r)/2;
if(seg.qry(mid, mid) > val) l = mid+1;
else r = mid;
}
return l;
}
signed main() {
int n, ans=0;
cin >> n;
seg.init(100000);
vector<pair<int, int>> v;
for(int i=1; i<=n; i++) {
int h, sa;
cin >> h >> sa;
v.push_back({h, sa});
}
sort(v.begin(), v.end());
for(auto i: v) {
int h = i.first, sa = i.second;
int val = seg.qry(h-sa+1, h-sa+1);
if(val > seg.qry(h, h)) {
int l = h, r = lbound(val-1, h);
sa -= l-r+1;
seg.upd(r, l, 1);
}
int l = lbound(val, h);
seg.upd(l, l+sa-1, 1);
}
for(int i=1; i<=100000; i++) {
int t = seg.qry(i, i);
ans += t*(t-1)/2;
}
cout << ans;
}
