import java.util.Scanner;

public class OmoritoTenbin {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int N = s.nextInt(),rest = 0;
		int[][] W = new int[N][2];
		for(int i = 0;i < N ;i++){
			W[i][0] = s.nextInt();
			rest += W[i][0];
			W[i][1] = 1;
		}
		s.close();
		if(rest%2 == 1){
			System.out.println("impossible");
		}else{
			rest /=2;
			int near = rest,k = 0;
			for(int i = 0;i < N;i++){
				if(W[i][1] != 0 &&Math.abs(near) > Math.abs(rest - W[i][0])){
					near = rest - W[i][0];
					k = i;
				}
				rest = Math.abs(near);
				W[k][1] = 0;
			}
			if(near == 0){
				System.out.println("possible");
			}else if(near < 0){
				for(int i = 0;i < N;i++){
					if(W[i][1] == 0){
						for(int j = i+1;j<N;j++){
							if(W[i][1] == 1 &&(W[i][0]+near == W[j][0] ||W[i][0] == near + W[j][0])){
								near = 0;
								break;
							}
						}
					}
					if(near == 0){
						break;
					}
				}
				if(near != 0){
					System.out.println("impossible");
				}
			}			
		}
	}
}