n = int(input())
R = -1
maxch = 0
maxnech = 0
minch = 10001
minnech = 10001

for i in range(n):
    x = int(input())
    if x > maxch and x % 2 == 0:
        maxch = x
    if x > maxnech and x % 2 != 0:
        maxnech = x
    if x < minch and x % 2 == 0:
        minch = x
    if x < minnech and x % 2 != 0:
        minnech = x
if maxch != 0 and maxnech != 0 and minch != 10001 and minnech != 10001:
    if maxch - minnech > maxnech - minnech:
        R = maxch - minnech
    else:
        R = maxnech - minnech
print(R)