#include <iostream>

#include <string>

#define MAXN 50

using namespace std;

struct node

{

    node * l;

    node * r;

    bool boo;

    node()

    {

        l = NULL;

        r = NULL;

        boo = false;

    }

};

bool ans;

int _index;

node res[*MAXN+];

node * insert(node * root,string s,int index,int len)

{

    if(s[index] == '')

    {

        if(root->l == NULL)

        {

            root->l = &res[_index ++];

            root->l->boo = false;

            root->l->l = root->l->r = NULL;

            if(index == len-)

            {

                root->l->boo = true;

                return root;

            }

        }

        else

        {

            if(index == len-)

            {

                ans = false;

                return root;

            }

            if(root->l->boo == true)

            {

                ans = false;

                return root;

            }

        }

        root->l = insert(root->l,s,index+,len);

        return root;

    }

    else

    {

        if(root->r == NULL)

        {

            root->r = &res[_index ++];

            root->r->boo = false;

            root->r->l = root->r->r = NULL;

            if(index == len-)

            {

                root->r->boo = true;

                return root;

            }

        }

        else

        {

            if(index == len-)

            {

                ans = false;

                return root;

            }

            if(root->r->boo == true)

            {

                ans = false;

                return root;

            }

        }

        root->r = insert(root->r,s,index+,len);

        return root;

    }

}

int main()

{

    //freopen("acm.acm","r",stdin);

    string s;

    int time = ;

    while(cin>>s)

    {

        _index = ;

        ans = true;

        node * root = &res[_index ++];

        root->boo = false;

        root->l = root->r = NULL;

        if(ans)

        {

            root = insert(root,s,,s.length());

        }

        while(cin>>s)

        {

            if(s == "")

            {

                break;

            }

            if(ans)

            {

                root = insert(root,s,,s.length());

            }

        }

        cout<<"Set "<<++ time;

        if(ans == false)

        {

            cout<<" is not immediately decodable"<<endl;

        }

        else

        {

            cout<<" is immediately decodable"<<endl;

        }

    }

}