#include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     vector<bool> primes(n + 1, 1);     primes[0] = primes[1] = 0;     for (int i = 2; i <= n; ++i) {       if (!primes[i]) continue;       for (int j = i * i; j <= n; j += i) primes[j] = 0;     }     vector<int> quest;     for (int i = 2; i <= n; ++i) {       if (!primes[i]) continue;       int k = i;       do {         quest.push_back(k);         k *= i;       } while (k <= n);     }     cout << quest.size() <<   n ;     for (int i = 0; i < quest.size(); ++i) cout << quest[i] <<    ;     return 0;   }   