func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     set<int> st;     for (int i = 2; i <= n; i++) {       int a = i;       for (int j = 2; j * j <= a; j++) {         int num = 1;         while (a % j == 0 and a > 1) {           a /= j;           num *= j;         }         if (num != 1) st.insert(num);       }       if (a > 1) st.insert(a);     }     cout << st.size() << endl;     for (auto item : st) cout << item <<    ;   }   