func_code_string: #include <bits/stdc++.h>   using namespace std;   int res[100005], sz;   bool prime[100005], used[100005];   int main() {     int n;     cin >> n;     for (int p = 2; p <= n / 2; ++p) {       if (prime[p]) continue;       for (int j = p; j <= n; j += p) prime[j] = 1;       if (p == 2) continue;       int len = 0;       for (int j = p; j <= n; j += p) {         if (j == 2 * p) continue;         if (used[j]) continue;         used[j] = 1;         res[sz++] = j;         len++;       }       if (len & 1) {         res[sz++] = 2 * p;         used[2 * p] = 1;       }     }     for (int i = 2; i <= n; i += 2)       if (!used[i]) res[sz++] = i;     cout << sz / 2 << endl;     for (int i = 0; i + 1 < sz; i += 2) printf( %d %d n , res[i], res[i + 1]);     return 0;   }   