func_code_string: #include <bits/stdc++.h>   inline int read() {     int data = 0, w = 1;     char ch = getchar();     while (ch !=  -  && (ch <  0  || ch >  9 )) ch = getchar();     if (ch ==  - ) w = -1, ch = getchar();     while (ch >=  0  && ch <=  9 ) data = data * 10 + (ch ^ 48), ch = getchar();     return data * w;   }   const int N(205), LIM(20010), M(20000), INF(0x3f3f3f3f);   struct edge {     int next, to, cap;   } e[N * N * 2];   int n, A[N], not_prime[LIM], head[N], e_num = -1, lev[N], cur[N], S, T;   inline void Add(int from, int to, int cap) {     e[++e_num] = (edge){head[from], to, cap}, head[from] = e_num;     e[++e_num] = (edge){head[to], from, 0}, head[to] = e_num;   }   void Init() {     not_prime[1] = 1;     for (int i = 2; i <= M; i++)       if (!not_prime[i])         for (int j = i * i; j <= M; j += i) not_prime[j] = 1;   }   int bfs() {     std::queue<int> Q;     Q.push(S);     memset(lev, 0, (T + 1) << 2), lev[S] = 1;     while (!Q.empty()) {       int x = Q.front();       Q.pop();       for (int i = head[x]; ~i; i = e[i].next) {         int to = e[i].to;         if (!e[i].cap || lev[to]) continue;         lev[to] = lev[x] + 1, Q.push(to);       }     }     return lev[T];   }   int dfs(int x, int f) {     if (x == T || !f) return f;     int ans = 0, cap;     for (int i = head[x]; ~i; i = e[i].next) {       int to = e[i].to;       if (e[i].cap && lev[to] == lev[x] + 1) {         cap = dfs(e[i].to, std::min(f - ans, e[i].cap));         e[i].cap -= cap, e[i ^ 1].cap += cap, ans += cap;         if (ans == f) break;       }     }     if (!ans) lev[x] = 0;     return ans;   }   int Dinic() {     int ans = 0;     while (bfs()) memcpy(cur, head, (T + 1) << 2), ans += dfs(S, INF);     return ans;   }   std::vector<int> cir[N];   int tot, vis[N];   void find(int x) {     if (1 <= x && x <= n) cir[tot].push_back(x);     vis[x] = 1;     for (int i = head[x]; ~i; i = e[i].next)       if (!vis[e[i].to] && e[i | 1].cap == 1) find(e[i].to);   }   int main() {     memset(head, -1, sizeof head);     Init(), n = read(), S = 0, T = n + 1;     int p = 0, q = 0;     for (int i = 1; i <= n; i++) A[i] = read(), ((A[i] & 1) ? ++p : ++q);     if (p != q) return puts( Impossible ), 0;     for (int i = 1; i <= n; i++)       if (A[i] & 1)         for (int j = (Add(S, i, 2), 1); j <= n; j++) {           if (!not_prime[A[i] + A[j]]) Add(i, j, 1);         }       else         Add(i, T, 2);     if (Dinic() != n) return puts( Impossible ), 0;     for (int i = 1; i <= n; i++)       if (!vis[i]) ++tot, find(i);     printf( %d n , tot);     for (int i = 1; i <= tot; i++, puts(  )) {       printf( %lu  , cir[i].size());       for (int j : cir[i]) printf( %d  , j);     }     return 0;   }   