def main():
    import sys
    input = sys.stdin.read().split()
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    A = list(map(int, input[ptr:ptr+N]))
    ptr += N
    B = list(map(int, input[ptr:ptr+N]))
    
    sum_A = sum(A)
    sum_B = sum(B)
    
    if N == 2:
        if sum_A != sum_B:
            print(-1)
            return
        delta = B[0] - A[0]
        x = abs(delta)
        k0 = (x + (B[0] - A[0])) // 2
        k1 = (x + (B[1] - A[1])) // 2
        if k0 >= 0 and k1 >= 0 and (k0 + k1) == x:
            print(x)
        else:
            print(-1)
        return
    else:
        numerator = sum_B - sum_A
        denominator = 2 - N
        if denominator == 0:
            print(-1)
            return
        if numerator % denominator != 0:
            print(-1)
            return
        x = numerator // denominator
        if x < 0:
            print(-1)
            return
        valid = True
        for a, b in zip(A, B):
            temp = x + (b - a)
            if temp < 0 or temp % 2 != 0:
                valid = False
                break
            k_i = temp // 2
            if k_i < 0:
                valid = False
                break
        if valid:
            print(x)
        else:
            print(-1)
    
if __name__ == "__main__":
    main()