CodeForces 1081B Farewell Party

B - Farewell Party

https://codeforces.com/contest/1081/problem/B

Description

Chouti and his classmates are going to the university soon. To say goodbye to each other, the class has planned a big farewell party in which classmates, teachers and parents sang and danced.

Chouti remembered that n persons took part in that party. To make the party funnier, each person wore one hat among n kinds of weird hats numbered 1,2,…n. It is possible that several persons wore hats of the same kind. Some kinds of hats can remain unclaimed by anyone.

After the party, the i-th person said that there were ai persons wearing a hat differing from his own.

It has been some days, so Chouti forgot all about others’ hats, but he is curious about that. Let bi be the number of hat type the i-th person was wearing, Chouti wants you to find any possible b1,b2,…,bn that doesn’t contradict with any person’s statement. Because some persons might have a poor memory, there could be no solution at all.

Input

The first line contains a single integer n (1≤n≤105), the number of persons in the party.

The second line contains n integers a1,a2,…,an (0≤ai≤n−1), the statements of people.

Output

If there is no solution, print a single line "Impossible".

Otherwise, print “Possible” and then n integers b1,b2,…,bn (1≤bi≤n).

If there are multiple answers, print any of them.

Sample Input

3

0 0 0

5

3 3 2 2 2

4

0 1 2 3

Sample Output

Possible

1 1 1

Possible

1 1 2 2 2

Impossible

Hint

In the answer to the first example, all hats are the same, so every person will say that there were no persons wearing a hat different from kind 1.

In the answer to the second example, the first and the second person wore the hat with type 1 and all other wore a hat of type 2.

So the first two persons will say there were three persons with hats differing from their own. Similarly, three last persons will say there were two persons wearing a hat different from their own.

In the third example, it can be shown that no solution exists.

In the first and the second example, other possible configurations are possible.

#include<stdio.h>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=100005;
int n,k=1,flag=0;
int sum[maxn],num[maxn],num1[maxn],ans[maxn],cou[maxn],dis[maxn];
void check()//检查ans数组是否符合题目意思 
{
	for(int i=1;i<=n;i++)
		cou[ans[i]]++;//计算和自己帽子相同的数量 
	for(int i=1;i<=n;i++)
		if(cou[ans[i]]+sum[i]!=n) flag=1;
	//如果看见的不同的冒子的数量加上和自己相同数量不等于n则不可能 
}
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&sum[i]);
		num[sum[i]]=n-sum[i];//和自己帽子相同的数量 
		cou[sum[i]]++;//帽子数为sum[i]的人的数量 
	}
	for(int i=1;i<=n;i++)
	{
		if(num[sum[i]]>cou[sum[i]])
			flag=1;
		num1[sum[i]]=num[sum[i]];
	}
	dis[sum[1]]=ans[1]=1;
	for(int i=2;i<=n;i++)
	{
		if(dis[sum[i]]==0) {
			ans[i]=dis[sum[i]]=++k;
		}
		else {
			if(num[sum[i]]==cou[sum[i]]) {
					ans[i]=dis[sum[i]];
			}
			else {
				if(num[sum[i]]>1) {
					ans[i]=dis[sum[i]];
					num[sum[i]]--;
				}
				else {
					ans[i]=dis[sum[i]]=++k;
					num[sum[i]]=num1[sum[i]];
				}
			}
		}
	}
	fill(cou,cou+(n+1),0);//fill函数归零 
	check();
	if(k>n||flag)
		printf("Impossible\n");
	else {
		printf("Possible\n");
		for(int i=1;i<=n;i++)
			printf("%d ",ans[i]);
		printf("\n");
	}
	return 0;
}