N = int(raw_input()) W = map(int,raw_input().split()) sumW = sum(W) print sumW W.sort() if sumW % 2 == 1: print 'impossible' else: s = 0 i = 0 while s < sumW /2: s += W[i] i += 1 if s == sumW / 2: print 'possible' else: print 'impossible'