//Optional FAST

//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,fma,abm,mmx,avx,avx2,tune=native")

//Required Libraries

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/detail/standard_policies.hpp>

//Required namespaces

using namespace std;
using namespace __gnu_pbds;

//Required defines

#define endl '\n'

#define READ(X) cin>>X;
#define READV(X) long long X; cin>>X;
#define READAR(A,N) long long A[N]; for(long long i=0;i<N;i++) {cin>>A[i];}
#define rz(A,N) A.resize(N);
#define sz(X) (long long)(X.size())
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define FORI(a,b,c) for(long long a=b;a<c;a++)
#define FORD(a,b,c) for(long long a=b;a>c;a--)

//Required typedefs

typedef tree<long long,null_type,less<long long>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
typedef tree<long long,null_type,greater<long long>,rb_tree_tag,tree_order_statistics_node_update> ordered_set1;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<long long,long long> pll;

//Required Constants

const long long inf=(long long)1e18;
const long long MOD=(long long)(1e9+7);
const long long INIT=(long long)(1e6+1);
const long double PI=3.14159265358979;

// Required random number generators

// mt19937 gen_rand_int(chrono::steady_clock::now().time_since_epoch().count());
// mt19937_64 gen_rand_ll(chrono::steady_clock::now().time_since_epoch().count());

//Required Functions

ll power(ll x,ll y) 
{ 
    if (y == 0) 
        return 1; 
    ll p = power(x, y/2) % MOD; 
    p = (p * p) % MOD; 
  
    return (y%2 == 0)? p : (x * p) % MOD; 
}
ll modInverse(ll a) 
{ 
   return power(a,MOD-2); 
   
}

//Work

int main()
{
    #ifndef ONLINE_JUDGE
    if (fopen("INPUT.txt", "r"))
    {
        freopen ("INPUT.txt" , "r" , stdin);
        //freopen ("OUTPUT.txt" , "w" , stdout);
    }
    #endif
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    clock_t clk;
    clk = clock();
//-----------------------------------------------------------------------------------------------------------//

    READV(N);
    READAR(A,N);
    sort(A,A+N);
    ll mx=A[N-1];
    if(N==2)
    {
        if(A[0]!=1)
        {
            cout<<"Impossible"<<endl;
        }
        else
        {
            cout<<"Possible"<<endl;
        }
    }
    else
    {
        bool ok=true;
        if(A[0]!=(A[N-1]+1)/2)
        {
            ok=false;
        }
        else
        {
            FORD(i,mx,0)
            {
                if(i==mx-i)
                {
                    ll cnt=0;
                    FORI(j,0,N)
                    {
                        if(A[j]==i)
                        {
                            cnt++;
                        }
                    }
                    if(cnt!=1)
                    {
                        ok=false;
                        break;
                    }
                }
                else if(A[0]==i || A[0]==mx-i)
                {
                    ll cnt=0;
                    FORI(j,0,N)
                    {
                        if(A[j]==max(mx-i,i))
                        {
                            cnt++;
                        }
                    }
                    if(cnt!=2)
                    {
                        ok=false;
                        break;
                    }
                }
                else
                {
                    ll cnt=0;
                    FORI(j,0,N)
                    {
                        if(A[j]==max(mx-i,i))
                        {
                            cnt++;
                        }
                    }
                    if(cnt<2)
                    {
                        ok=false;
                        break;
                    }
                }
                
            }
        }
        
        if(!ok)
        {
            cout<<"Impossible"<<endl;
        }
        else
        {
            cout<<"Possible"<<endl;
        }

    }
    

//-----------------------------------------------------------------------------------------------------------//


    clk = clock() - clk;
    cerr << fixed << setprecision(6) << "Time: " << ((double)clk)/CLOCKS_PER_SEC << endl;

    return 0;
}

Measured memory_bytes: 3804