#include<stdio.h>
#include <stdlib.h>

int main() {
	int dataNum = 0;
	int data[1000];
	char str;
	int total = 0;
	int harf = 0;

	scanf("%d", &dataNum);

	for (int i = 0; i < dataNum; i++)
		data[i] = 0;

	for (int i = 0; str != '\n'; ) {
		str = getchar();
		if (str == '\0')
			i++;
		else
			data[i] = data[i] * 10 + (int)str - (int)'0';
	}

	// 合計値を求める
	for (int i = 0; i < dataNum; i++)
		total += data[i];

	// 偶数でない場合はimpossible
	if (total % 2 == 0) {
		printf("impossible");
		return 0;
	}

	// 半分の値を求める
	harf = total / 2;

	printf("possible");

	return 0;
}