#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// BeginCodeSnip{Binary Indexed Tree (from the module)}
template <class T> class BIT {
private:
int size;
vector<T> bit;
vector<T> arr;
public:
BIT(int size) : size(size), bit(size + 1), arr(size) {}
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;
}
};
// EndCodeSnip
int main() {
int n;
cin >> n;
vector<int> h(n), k(n);
for (int i = 0; i < n; i++) { cin >> h[i] >> k[i]; }
vector<int> ord(n);
iota(begin(ord), end(ord), 0);
sort(begin(ord), end(ord), [&](int i, int j) -> bool { return h[i] < h[j]; });
const int max_h = *max_element(begin(h), end(h));
BIT<int> bit(max_h + 1);
/** @return first index with bit.pref_sum(i) < val */
const auto first_val = [&](int val, int high) {
int low = 0;
while (low < high) {
int mid = low + (high - low) / 2;
int cur_val = bit.pref_sum(mid);
(cur_val < val) ? high = mid : low = mid + 1;
}
return low;
};
for (int i : ord) {
int last = h[i] - k[i];
int val = bit.pref_sum(last);
int idx_1 = first_val(val, h[i]);
int idx_2 = first_val(val + 1, h[i]);
bit.add(idx_1, 1);
bit.add(h[i], -1);
bit.add(idx_2, 1);
bit.add(idx_2 + k[i] - (h[i] - idx_1), -1);
}
ll res = 0;
for (int i = 0; i < max_h; i++) {
int sail_num = bit.pref_sum(i);
res += 1ll * sail_num * (sail_num - 1) / 2;
}
cout << res << endl;
}
