Ndata = int(input());
itiran = input();
itirandata = itiran.split(" ");
itirannumdata = sorted(itirandata,key= int);
sumtmp = 0;
results = 0;
result = "";
kanren = 0;

for indexer in range(0,Ndata):
	sumtmp = sumtmp + int(itirannumdata[indexer]);


if sumtmp % 2 == 0:
    sumtmp = int(sumtmp / 2);
    firstkansu = Ndata -1;
    while firstkansu >= 0:
        kanren = int(itirannumdata[firstkansu]);
        results = results + kanren;
        if results > sumtmp:
            results = results - kanren;
            
        if firstkansu == 0 and results == sumtmp:
            result = "possible";
        else:
            result = "impossible";
            
        firstkansu = firstkansu - 1;
else:
	result = "impossible";
	
print(result);