#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
#include <chrono>
#include <fstream>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
struct node{
int s, e, m, val;
node *l, *r;
node(int S, int E){
s = S, e = E, m = (s+e)/2;
val=0;
if (s!=e){
l = new node(s, m);
r = new node(m+1, e);
}
}
void up(int ind, int nv){
if (s==e)val+=nv;
else{
if (ind<=m)l->up(ind, nv);
else r->up(ind, nv);
val = min(l->val, r->val);
}
}
int bs(int left, int right){
if (s==left&&e==right)return val;
if (right<=m)return l->bs(left, right);
if (left>m)return r->bs(left, right);
return min(l->bs(left, m), r->bs(m+1, right));
}
int query(int i){
if (s==e)return val;
if (i<=m)return l->query(i);
return r->query(i);
}
}*st;
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, ans=0;
cin>>n;
vector<pii> vect(n);
st = new node(0, 100005);
for (int i=0; i<n; ++i)cin>>vect[i].fi>>vect[i].se;
sort(vect.begin(), vect.end());
for (int i=0; i<n; ++i){
int left=1, high=vect[i].fi-vect[i].se+2;
while (left+1<high){
int mid=(left+high)/2;
if (st->bs(mid, vect[i].fi-vect[i].se+1))left=mid;
else high=mid;
}
int low=vect[i].fi-vect[i].se, right=100005;
while (low+1<right){
int mid=(low+right)/2;
if (st->bs(vect[i].fi-vect[i].se+1, mid))right=mid;
else low=mid;
}
int c=min(right-vect[i].fi+vect[i].se-1, vect[i].se);
st->up(left, 1);
st->up(left+c, -1);
if (right<=vect[i].fi){
st->up(right, 1);
st->up(vect[i].fi+1, -1);
}
}
for (int i=1, sum=0; i<=n; ++i)sum+=st->query(i), ans+=sum*(sum-1)/2;
cout<<ans;
}
