func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     int a, b;     int s[4010];     cin >> n;     memset(s, 0, sizeof(s));     for (int i = 0; i < n; i++) {       cin >> a >> b;       s[a + b]++;       s[a - b + 3000]++;     }     long long sum = 0;     for (int i = 0; i <= 4000; i++) {       if (s[i] > 1) sum += (s[i] * (s[i] - 1) / 2);     }     cout << sum << endl;     return 0;   }   