#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAXN = 1e5;
struct Data { int H, K; };
int N;
Data A[MAXN+10];
ll tree[4*MAXN+10], ans;
ll getval(int node, int tl, int tr, int pos)
{
if(tl==tr) return tree[node];
int mid=tl+tr>>1;
if(pos<=mid) return tree[node]+getval(node*2, tl, mid, pos);
else return tree[node]+getval(node*2+1, mid+1, tr, pos);
}
void update(int node, int tl, int tr, int l, int r)
{
if(r<tl || tr<l) return;
if(l<=tl && tr<=r) { tree[node]++; return; }
int mid=tl+tr>>1;
update(node*2, tl, mid, l, r);
update(node*2+1, mid+1, tr, l, r);
}
int main()
{
int i, j;
scanf("%d", &N);
for(i=1; i<=N; i++) scanf("%d%d", &A[i].H, &A[i].K);
sort(A+1, A+N+1, [&](const Data &p, const Data &q) { return p.H<q.H; });
for(i=1; i<=N; i++)
{
int lo, hi, l, r;
ll val=getval(1, 1, MAXN, A[i].H-A[i].K+1);
lo=0, hi=A[i].H-A[i].K+1;
while(lo+1<hi)
{
int mid=lo+hi>>1;
if(val==getval(1, 1, MAXN, mid)) hi=mid;
else lo=mid;
}
l=hi;
lo=A[i].H-A[i].K+1, hi=A[i].H+1;
while(lo+1<hi)
{
int mid=lo+hi>>1;
if(val==getval(1, 1, MAXN, mid)) lo=mid;
else hi=mid;
}
r=lo;
update(1, 1, MAXN, r+1, A[i].H);
update(1, 1, MAXN, l, l+A[i].K-A[i].H+r-1);
//printf("%d %d\n", l, r);
//for(j=1; j<=10; j++) printf("%lld ", getval(1, 1, MAXN, j)); printf("\n");
}
for(i=1; i<=MAXN; i++)
{
ll t=getval(1, 1, MAXN, i);
ans+=t*(t-1)/2;
}
printf("%lld", ans);
}
