func_code_string: #include <bits/stdc++.h>   using namespace std;   struct SUBS {     string _s;     int l, r;     SUBS() {}     SUBS(string s, int l, int r) : _s(s), l(l), r(r) {}     bool operator<(const SUBS& subs) const { return _s > subs._s; }   };   priority_queue<SUBS> pq;   string s;   long long n, k;   int main() {     cin >> s;     cin >> k;     n = s.length();     if (2 * k > n * (n + 1)) {       cout <<  No such line.  << endl;       return 0;     }     for (int i = 0; i < n; i++) pq.push(SUBS(s.substr(i, 1), i, i + 1));     SUBS subs;     for (int i = 0; i < k; i++) {       subs = pq.top();       pq.pop();       if (subs.r < n) {         int len = subs.r - subs.l;         pq.push(SUBS(s.substr(subs.l, len + 1), subs.l, subs.r + 1));       }     }     cout << subs._s << endl;   }   