#include<bits/stdc++.h>
using namespace std;
#define debug(...) 40
using ll = long long;
using pii = pair<int, int>;
using db = long double;
#define int long long
#define el cout << '\n'
#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FOD(i, a, b) for (int i = (a); i >= (b); i--)
#define REP(i, n) for (int i = 0; i < (n); i++)
template <class T1, class T2>bool chmax(T1 &a, T2 b){return a < b ? a = b, 1 : 0;}
template <class T1, class T2>bool chmin(T1 &a, T2 b){return a > b ? a = b, 1 : 0;}
long long rng() {
static std::mt19937 gen(
std::chrono::steady_clock::now().time_since_epoch().count());
return std::uniform_int_distribution<long long>(0, INT64_MAX)(gen);
}
const int maxn = 1e5 + 5;
const int mod = 1e9 + 7;
template <class T> class BIT {
private:
int n;
vector<T> bit;
vector<T> arr;
public:
BIT(int n) : n(n), bit(n + 1), arr(n) {}
void set(int k, T val) { add(k, val - arr[k]); }
void add(int k, T val) {
arr[k] += val;
k++;
for (; k <= n; k += k & -k) { bit[k] += val; }
}
T query(int a, int b) {
b++;
T s = 0;
for (; a > 0; a -= a & -a) { s -= bit[a]; }
for (; b > 0; b -= b & -b) { s += bit[b]; }
return s;
}
};
template <class T> class RURQBIT {
private :
int n;
vector<T> a;
BIT<T> b, c;
public :
RURQBIT(int n) : n(n), a(n + 1), b(n + 2), c(n + 2){}
void build(vector<int> &v){
for(int i = 1; i <= v.size(); i++){
a[i] = v[i - 1];
b.set(i, a[i] - a[i - 1]);
c.set(i, i * (a[i] - a[i - 1]));
}
}
void add(int l, int r, T v){
if(l > r) return;
b.add(l, v);
b.add(r + 1, -v);
c.add(l, l * v);
c.add(r + 1, -(r + 1) * v);
}
T query(int l, int r){
T rs = (r + 1) * b.query(1, r) - c.query(1, r);
T ls = l * b.query(1, l - 1) - c.query(1, l - 1);
return rs - ls;
}
T query(int l){
return query(l, l);
}
};
RURQBIT<int> bit(maxn);
void solve(){
int n;
cin >> n;
vector<pii> a(n);
for (int i = 0; i < n; i++){
cin >> a[i].fi >> a[i].se;
}
sort(all(a));
for (int i = 0; i < n; i++){
auto [h, k] = a[i];
debug(h, k);
int val = bit.query(h - k + 1);
int lo = 1, hi = h;
while(lo < hi){
int mid = lo + (hi - lo + 1) / 2;
if (bit.query(mid) >= val) lo = mid;
else hi = mid - 1;
}
int l1 = lo;
lo = 1, hi = h;
while(lo < hi){
int mid = lo + (hi - lo) / 2;
if (bit.query(mid) <= val) hi = mid;
else lo = mid + 1;
}
int l2 = lo;
bit.add(l1 + 1, h, 1);
// h - l1
bit.add(l2, l2 + k - 1 - (h - l1), 1);
}
int ans = 0;
for (int i = 1; i <= a[i - 1].fi; i++){
int val = bit.query(i);
ans += val * (val - 1) / 2;
}
cout << ans;
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int tests = 1;
// cin >> tests;
for (int _ = 1; _ <= tests; _++){
cerr << "- Case #" << _ << ": \n";
solve();
// el;
}
return 0;
}
