#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
using ll = long long;
template <class T> class BIT {
private:
int size;
int LOGN = 0;
vector<T> bit;
vector<T> arr;
public:
BIT(int size) : size(size), bit(size + 1), arr(size) {
LOGN = 0;
while ((1 << (LOGN+1)) <= size) {
LOGN++;
}
}
void set(int ind, T val) { add(ind, val - arr[ind]); }
void add(int ind, T val) {
arr[ind] += val;
ind++;
for (; ind <= size; ind += ind & -ind) { bit[ind] += val; }
}
T pref_sum(int ind) {
ind++;
T total = 0;
for (; ind > 0; ind -= ind & -ind) { total += bit[ind]; }
return total;
}
int first_below(int v) {
int sum = 0, pos = 0;
for (int k = LOGN; k >= 0; --k) {
int nxt = pos + (1 << k);
if (nxt <= size && sum + bit[nxt] >= v) {
sum += bit[nxt];
pos = nxt;
}
}
return pos;
}
};
int main() {
int n; cin >> n;
vector<pair<int, int>> poles;
int mx = 0;
for (int i = 0; i < n; i++) {
int a, b; cin >> a >> b;
mx = max(mx, a);
poles.push_back({a, b});
}
sort(poles.begin(), poles.end());
BIT<int> bit(mx+1);
for (int i = 0; i < n; i++) {
int h = poles[i].f;
int k = poles[i].s;
int v = bit.pref_sum(h-k);
int idx1 = min(h, bit.first_below(v));
int idx2 = min(h, bit.first_below(v+1));
bit.add(idx1, 1);
bit.add(h, -1);
bit.add(idx2, 1);
bit.add(idx2 + k - (h - idx1), -1);
}
ll ans = 0;
for (int i = 0; i < n; i++) {
ll x = bit.pref_sum(i);
ans += (x*(x-1))/2;
}
cout << ans;
}
