description: There are n candles on a Hanukkah menorah, and some of its candles are initially lit. We can describe which candles are lit with a binary string s, where the i-th candle is lit if and only if s_i=1.
  
  <image>
  
  Initially, the candle lights are described by a string a. In an operation, you select a candle that is currently lit. By doing so, the candle you selected will remain lit, and every other candle will change (if it was lit, it will become unlit and if it was unlit, it will become lit).
  
  You would like to make the candles look the same as string b. Your task is to determine if it is possible, and if it is, find the minimum number of operations required.
  
  Input
  
  The first line contains an integer t (1≤ t≤ 10^4) — the number of test cases. Then t cases follow.
  
  The first line of each test case contains a single integer n (1≤ n≤ 10^5) — the number of candles.
  
  The second line contains a string a of length n consisting of symbols 0 and 1 — the initial pattern of lights.
  
  The third line contains a string b of length n consisting of symbols 0 and 1 — the desired pattern of lights.
  
  It is guaranteed that the sum of n does not exceed 10^5.
  
  Output
  
  For each test case, output the minimum number of operations required to transform a to b, or -1 if it's impossible.
  
  Example
  
  Input
  
  
  5
  5
  11010
  11010
  2
  01
  11
  3
  000
  101
  9
  100010111
  101101100
  9
  001011011
  011010101
  
  
  Output
  
  
  0
  1
  -1
  3
  4
  
  Note
  
  In the first test case, the two strings are already equal, so we don't have to perform any operations.
  
  In the second test case, we can perform a single operation selecting the second candle to transform 01 into 11.
  
  In the third test case, it's impossible to perform any operations because there are no lit candles to select.
  
  In the fourth test case, we can perform the following operations to transform a into b: 
  
    1. Select the 7-th candle: 100010{\color{red}1}11→ 011101{\color{red} 1}00. 
    2. Select the 2-nd candle: 0{\color{red} 1}1101100→ 1{\color{red} 1}0010011. 
    3. Select the 1-st candle: {\color{red}1}10010011→ {\color{red}1}01101100. 
  
  
  
  In the fifth test case, we can perform the following operations to transform a into b: 
  
    1. Select the 6-th candle: 00101{\color{red}1}011→ 11010{\color{red}1}100 
    2. Select the 2-nd candle: 1{\color{red}1}0101100→ 0{\color{red}1}1010011 
    3. Select the 8-th candle: 0110100{\color{red}1}1→ 1001011{\color{red}1}0 
    4. Select the 7-th candle: 100101{\color{red}1}10→ 011010{\color{red}1}01 
solution: # cook your dish here
  import sys
  #import random
  from bisect import bisect_left as lb
  from bisect import bisect_right as rb
  from collections import deque
  #sys.setrecursionlimit(10**8)
  from queue import PriorityQueue as pq
  from math import gcd
  #import math
  input_ = lambda: sys.stdin.readline().strip("\r\n")
  ii = lambda : int(input_())
  il = lambda : list(map(int, input_().split()))
  ilf = lambda : list(map(float, input_().split()))
  lii = lambda : list(map(int, list(ip())))
  ip = lambda : input_()
  fi = lambda : float(input_())
  ap = lambda ab,bc,cd : ab[bc].append(cd)
  li = lambda : list(input_())
  pr = lambda x : print(x)
  prinT = lambda x : print(x)
  f = lambda : sys.stdout.flush()
  inv =lambda x:pow(x,mod-2,mod)
  dx = [0,0,1,-1]
  dy = [1,-1,0,0]
  mod = 10**9 + 7
  mod1 = 998244353
  
  for _ in range (ii()) :
      n = ii()
      a = list(ip())
      b = list(ip())
  
      if (a == b) :
          print(0)
          continue
  
      x = a.count('0')
      if (x == n) :
          print(-1)
          continue
  
      t = 0
      t1 = 0
  
      for i in range (n) :
          if (a[i] == '1' and b[i] == '0') :
              t += 1
          if (a[i] == '0' and b[i] == '1') :
              t1 += 1
  
  
      y = n - x
  
      t,t1 =t1,t 
      t2 = x - t
      t3 = y - t1
  
      ans = 10**13
  
      #print(t,t1,t2,t3)
  
      if (t3 == t2 + 1) :
          ans = min(ans,t3 + t2)
  
      if (t1 == t) :
          ans = min(ans, t + t1)
  
      if (ans == 10**13) :
          print(-1)
      else :
          print(ans)
      
      
  
      
  