import std.stdio;
import std.string, std.conv, std.array, std.algorithm;
import std.uni, std.math, std.container;
import core.bitop, std.datetime;

void main(){
    int N = readln.chomp.to!int;
    auto W = readln.split.to!(int[]);
    auto H = W.sum;

    if(H % 2){
        writeln("impossible");
        return;
    }

    H /= 2;
    auto maxW = W.fold!(max);

    auto dp = new bool[](maxW * N + 1);
    dp[0] = true;

    foreach(i ; 1 .. N + 1){
        foreach_reverse(w ; W[i - 1] .. maxW * N + 1){
            dp[w] |= dp[w - W[i - 1]];
        }
    }

    if(dp[H]) writeln("possible");
    else writeln("impossible");
}