func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long iinf = 1e9 + 10;   const long long inf = 1ll << 60;   const long long mod = 1e9 + 87;   void GG() {     cout <<  0 n ;     exit(0);   }   long long mpow(long long a, long long n, long long mo = mod) {     long long re = 1;     while (n > 0) {       if (n & 1) re = re * a % mo;       a = a * a % mo;       n >>= 1;     }     return re;   }   long long inv(long long b, long long mo = mod) {     if (b == 1) return b;     return (mo - mo / b) * inv(mo % b, mo) % mo;   }   const long long maxn = 1e6 + 5;   unsigned long long H[maxn];   bool np[maxn];   unsigned long long val[maxn];   long long n;   void RET(vector<long long> no) {     vector<long long> yay(n + 1);     for (long long t : no) yay[t] = 1;     cout << n - (long long)no.size() <<   n ;     for (long long i = 1; i <= n; ++i) {       if (!yay[i]) cout << i <<    ;     }     cout <<   n ;     exit(0);   }   signed main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     ;     mt19937_64 rnd(time(0));     for (long long i = 0; i < maxn; ++i) {       val[i] = rnd();     }     for (long long i = 2; i < maxn; ++i) {       if (!np[i]) {         for (long long j = i; j < maxn; j += i) {           if (j != i) np[j] = 1;           long long r = j;           while (r % i == 0) {             r /= i;             H[j] ^= val[i];           }         }       }     }     cin >> n;     for (long long i = 1; i < maxn; ++i) H[i] ^= H[i - 1];     unsigned long long all = 0;     for (long long i = 1; i <= n; ++i) all ^= H[i];     if (all == 0) {       RET({});     }     for (long long i = 1; i <= n; ++i) {       if (H[i] == all) {         RET({i});       }     }     vector<pair<unsigned long long, long long> > v;     for (long long i = 1; i <= n; ++i) {       v.push_back({H[i], i});     }     sort(v.begin(), v.end());     for (long long i = 1; i <= n; ++i) {       long long at =           lower_bound(v.begin(), v.end(),                       pair<unsigned long long, long long>{H[i] ^ all, i + 1}) -           v.begin();       if (at < (long long)v.size() && (v[at].first == (H[i] ^ all))) {         RET({i, v[at].second});       }     }     assert(n % 2 == 1);     RET({n, n / 2, 2});   }   