func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1111;   int n;   string a[N], b[N];   int t[N];   int d;   std::set<pair<string, string> > res;   int main() {     cin >> n >> d;     for (int i = 0; i < n; i++) cin >> a[i] >> b[i] >> t[i];     for (int i = 0; i < n; i++)       for (int j = i + 1; j < n; j++) {         if (!(a[i] == b[j] && a[j] == b[i])) continue;         int m = min(t[i], t[j]);         int M = max(t[i], t[j]);         if (M - m <= 0 || M - m > d) continue;         res.insert(make_pair(a[i], b[i]));         res.insert(make_pair(b[i], a[i]));       }     cout << res.size() / 2 << endl;     for (set<pair<string, string> >::iterator it = res.begin(); it != res.end();          ++it) {       string s1 = it->first, s2 = it->second;       if (s1 < s2) cout << s1 <<     << s2 << endl;     }   }   