func_code_string: #include <bits/stdc++.h>   using namespace std;   set<pair<string, string> > m;   int n, z[2000], d, k, ans;   string a[2000], b[2000], zx[2000][5];   int main() {     cin >> n >> d;     for (int i = 0; i < n; i++) {       cin >> a[i];       cin >> b[i];       cin >> z[i];     }     for (int i = 0; i < n; i++)       for (int j = i + 1; j < n; j++)         if (z[j] - z[i] <= d) {           if (a[i] == b[j] && a[j] == b[i] && z[i] != z[j])             m.insert(make_pair(min(a[i], b[i]), max(a[i], b[i])));         } else           break;     cout << m.size() << endl;     for (set<pair<string, string> >::iterator i = m.begin(); i != m.end(); i++)       cout << i->first <<     << i->second << endl;     return 0;   }   