Submission #44694350

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

#define x first
#define y second
#define mp(x, y) make_pair(x, y)
#define fro(i, x, y) for(int i = (x);i <= (y);i++)
#define pre(i, x, y) for(int i = (x);i >= (y);i--)

typedef long long ll;
typedef __int128 lll;
typedef unsigned int uint;
typedef pair<int, int> PII;
typedef unsigned long long ull;

const int N = 1000010;
const int mod = 998244353;

int n, m, a[N], ton[N];

signed main()
{
    ios::sync_with_stdio(0), cin.tie(0);
    cin >> n;
    fro(i, 1, n) cin >> a[i];
    sort(a + 1, a + n + 1);
    fro(i, 1, n) ton[a[i]]++;
    int t = a[n];
    fro(i, 1, (t - 1) / 2)
        if(ton[i]) cout << "Impossible\n", exit(0);
    if(t % 2 == 0 && ton[t / 2] != 1)
        cout << "Impossible\n", exit(0);
    if(t % 2 != 0 && ton[t / 2 + 1] != 2)
        cout << "Impossible\n", exit(0);
    fro(i, (t + 1) / 2 + 1, t)
        if(ton[i] < 2) cout << "Impossible\n", exit(0);
    cout << "Possible\n";
    return 0;
}

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