N=int(input ())
W=[int(i) for i in input (). split ()]
H=0
nd=0
for i in range (N):
    H+=W[i]
if H%2==1:
    nd=2
else:
    H//=2
    W.sort(reverse=True)
    H-=W[0]
    W.pop(0)
    N-=1
U=0
i=0
S=[0]*N
while nd<1:
    while i<N and U<H:
        S[i]=1
        U+=W[0]
        i+=1
    if U==H:
        nd=1
    elif i<N:
        i-=1
        S[i]=0
        U-=W[i]
        i+=1
    else:
        i-=1
        while i>=0 and S[i]==1:
            S[i]=0
            U-=W[i]
            i-=1
        while i>=0 and S[i]==0:
            i-=1
        if i<0:
            nd=2
        else:
            S[i]=0
            U-=W[i]
            i+=1
if nd==2:
    p="impossible"
elif nd==1:
     p="possible"
print (p)