#include <bits/stdc++.h>
using namespace std;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    unordered_map<long long, long long> cnt;
    for (int i = 0; i < n; i++) {
        long long a, b;
        cin >> a >> b;
        cnt[a - b]++;
    }
    long long ans = 0;
    if (cnt.count(0)) {
        long long c = cnt[0];
        ans += c * (c - 1) / 2;
    }
    for (auto &p : cnt) {
        long long d = p.first;
        if (d > 0 && cnt.count(-d)) {
            ans += p.second * cnt[-d];
        }
    }
    cout << ans;
    return 0;
}
 

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1 2
4 3
2 1