string s, t;
vpii ev[4000007];
map<char, vi> lets, lett;
map<char, char> tr;
int T[4000007], SS[4000007];
vi S;
int z[4000007];

void calc()
{
    int n = s.size() + t.size() + 1;
    int l = 0, r = 0;
    for (int i = 1; i < n; ++i)
    {
        for (int j = 0; j < ev[i].size(); ++j)
            SS[ev[i][j].X] = ev[i][j].Y;
        if (i <= r)
            z[i] = min(r - i + 1, z[i - l]);
        while (i + z[i] < n && SS[z[i]] == SS[i + z[i]])
            ++z[i];
        if (i + z[i] - 1 > r)
            l = i, r = i + z[i] - 1;
    }
}

int solve()
{
    getline(cin, s);
    getline(cin, t);
    fill(T, T + MAXN, -1);
    fill(SS, SS + MAXN * 2, -1);
    for (int i = 0; i < s.size() + t.size() + 1; ++i)
        SS[i] = 0;
    SS[t.size()] = -228;
    forn(i, s.size())
    {
        if (!lets[s[i]].empty())
        {
            int l = lets[s[i]].back();
            int r = i;
            int len = (int)t.size();
            if (l > r - len)
            {
                if (r - len < 0)
                    SS[l + len + 1] = r - l;
                else
                    ev[r + 2].inb(mk(l + len + 1, r - l));
            }
        }
        lets[s[i]].inb(i);
    }
    forn(i, t.size())
    {
        if (!lett[t[i]].empty())
            SS[lett[t[i]].back()] = i - lett[t[i]].back();
        lett[t[i]].inb(i);
    }
    calc();
    int pos = -1;
    for (int i = 0; i < s.size() + t.size() + 1; ++i)
    {
        if (z[i] == t.size())
        {
            pos = i - t.size() - 1;
            break;
        }
    }
    if (pos == -1)
        puts("Impossible"), exit(0);
    puts("Possible");
    for (int i = pos; i < pos + t.size(); ++i)
    {
        tr[s[i]] = t[i - pos];
    }
    for (int i = 0; i < s.size(); ++i)
    {
        if (tr.find(s[i]) != tr.end())
        {
            cout << tr[s[i]];
        }
        else
        {
            cout << "?";
        }
    }
    return 0;
}