N=int(input())
A=[int(input()) for i in range(N)]
ANS=[-1]*N

QS=[set(range(N)) for i in range(N)]

for i in range(N):
    if A[i]<N:
        QS[A[i]].discard(i)

count=0
while count<N:
    flag=0
    for i in range(N):
        if len(QS[i])==1:
            x=QS[i].pop()
            ANS[x]=i
            count+=1

            for j in range(N):
                QS[j].discard(x)
            break

    else:
        for i in range(N):
            if QS[i]==set():
                continue
         
            x=QS[i].pop()

            ANS[x]=i
            count+=1
            QS[i]=set()
            for j in range(N):
                QS[j].discard(x)
            break
        else:
            print(-1)
            exit()
    
for ans in ANS:
    print(ans)