#include <bits/stdc++.h>
using namespace std;
const int inf = 1e9 + 333;
const long long linf = 1e18 + inf;
const int N = 200 + 5;
const int S = 200 + 1;
const int T = 200 + 2;
int n;
int a[N], d[N][N];
int prime(int x) {
  int sq = sqrt(x) + .5;
  for (int i = 2; i <= sq; i++)
    if (x % i == 0) return 0;
  return 1;
}
bool used[N];
bool dfs(int x) {
  if (x == T) return 1;
  used[x] = 1;
  for (int i = 1; i < N; i++) {
    if (!used[i] and d[x][i] and dfs(i)) {
      d[x][i]--;
      d[i][x]++;
      return 1;
    }
  }
  return 0;
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", a + i);
    if (a[i] & 1) {
      d[S][i] = 2;
    } else {
      d[i][T] = 2;
    }
  }
  for (int i = 1; i <= n; i++) {
    if (a[i] & 1) {
      for (int j = 1; j <= n; j++) {
        if (prime(a[i] + a[j])) {
          d[i][j] = 1;
        }
      }
    }
  }
  int ans = 0;
  for (;;) {
    memset(used, 0, sizeof(used));
    if (!dfs(S)) break;
    ans++;
  }
  if (ans != n) {
    puts("Impossible");
    return 0;
  }
  memset(used, 0, sizeof(used));
  vector<vector<int> > ansV;
  for (int i = 1; i <= n; i++) {
    if (!used[i] and a[i] % 2) {
      vector<int> v;
      used[i] = 1;
      v.push_back(i);
      int x;
      for (int j = 1; j <= n; j++) {
        if (d[j][i]) {
          x = j;
          break;
        }
      }
      while (!used[x]) {
        used[x] = 1;
        v.push_back(x);
        for (int j = 1; j <= n; j++) {
          if (a[x] % 2) {
            if (!used[j] and d[j][x]) {
              x = j;
              break;
            }
          } else {
            if (!used[j] and d[x][j]) {
              x = j;
              break;
            }
          }
        }
      }
      ansV.push_back(v);
    }
  }
  printf("%d\n", ansV.size());
  for (auto v : ansV) {
    printf("%d", v.size());
    for (auto x : v) {
      printf(" %d", x);
    }
    puts("");
  }
  return 0;
}
