func_code_string: #include <bits/stdc++.h>   using namespace std;   class substr {    public:     string str;     int id;     bool operator<(const substr &a) const { return str > a.str; }   };   priority_queue<substr> Q;   int main() {     string s;     int k, n;     cin >> s >> k;     n = s.length();     for (int i = 0; i < n; i++) {       substr a;       a.str = s[i];       a.id = i;       Q.push(a);     }     while (!Q.empty()) {       substr p;       p = Q.top();       Q.pop();       k--;       if (!k) {         cout << p.str << endl;         return 0;       }       if (p.id != n - 1) {         p.str = p.str + s[p.id + 1];         p.id = p.id + 1;         Q.push(p);       }     }     cout <<  No such line.  << endl;     return 0;   }   