#include <bits/stdc++.h>
using namespace std;
int A[205], P[405], N, C[405][405], T, U[20005], V[405], s, t = 201, f, n;
queue<int> Q;
vector<int> E[405], E2[405], B[405];
void dfs(int n, int r) {
  if (V[n]) return;
  B[T].push_back(n);
  V[n] = 1;
  for (int v : E2[n]) dfs(v, r);
}
int main() {
  for (int i = 2; i <= (20000); i++)
    if (!U[i])
      for (n = 2 * i; n <= 20000; n += i) U[n] = 1;
  cin >> N;
  for (int i = 1; i <= (N); i++) cin >> A[i];
  for (int i = 1; i <= (N); i++)
    for (int j = 1; j <= (N); j++)
      if (A[i] % 2 == 0 && A[j] % 2 == 1 && !U[A[i] + A[j]])
        E[i].push_back(j), E[j].push_back(i), C[i][j] = 1;
  for (int i = 1; i <= (N); i++) {
    if (A[i] % 2 == 0)
      E[s].push_back(i), C[s][i] = 2;
    else
      E[i].push_back(t), C[i][t] = 2;
  }
  while (1) {
    for (int i = 1; i <= (201); i++) V[i] = 0;
    Q.push(0);
    V[0] = 1;
    while (!Q.empty()) {
      int n = Q.front();
      Q.pop();
      for (int v : E[n])
        if (C[n][v] && !V[v]) V[v] = 1, P[v] = n, Q.push(v);
    }
    if (!V[t]) break;
    f++, n = t;
    while (n) {
      C[P[n]][n]--;
      C[n][P[n]]++;
      n = P[n];
    }
  }
  if (f < N) {
    cout << "Impossible";
    return 0;
  }
  for (int i = 1; i <= (201); i++) V[i] = 0;
  for (int i = 1; i <= (N); i++)
    if (A[i] % 2 == 0)
      for (int v : E[i])
        if (!C[i][v]) E2[i].push_back(v), E2[v].push_back(i);
  for (int i = 1; i <= (N); i++)
    if (!V[i]) T++, dfs(i, i);
  cout << T << "\n";
  for (int i = 1; i <= (T); i++) {
    cout << B[i].size() << " ";
    for (int k : B[i]) cout << k << " ";
    cout << "\n";
  }
}
