#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 lbs(int i){
if (s==e){
if (val&&s<=i)return s;
return -1;
}
int res=r->lbs(i);
if (res==-1)return l->lbs(i);
return res;
}
int rbs(int i){
if (s==e){
if (val&&s>=i)return s;
return LLONG_MAX/2;
}
int res=l->rbs(i);
if (res==LLONG_MAX/2)return r->rbs(i);
return res;
}
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, n+1);
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=max(1ll, st->lbs(vect[i].fi-vect[i].se+1)), right=min(n+1, st->rbs(vect[i].fi-vect[i].se+1)), c=min(right, vect[i].fi+1)-vect[i].fi+vect[i].se-1;
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;
}
