import math
for _ in range(int(input())):
    N=int(input())
    if N==0:
        print(0)
        continue
    m0=math.isqrt(N)
    for m in[m0-1,m0,m0+1]:
        if m<0:
            continue
        k=m^N
        if math.isqrt(k)==m:
            print(k)
            break
    else:
        print(-1)