public int solution100Gcd(int[] A, int[] B){
    int r = 0;

    for(int i = 0; i < A.length; i++){
      int a = A[i], b = B[i];
      if(a == b){
        r++;
      } else {
        int gcd = gcd(a, b);
        if( restFromDividingByGcd(a, gcd) == 1 &&
            restFromDividingByGcd(b, gcd) == 1){
            r++;
        }
      }
    }
    return r;
  }

  int restFromDividingByGcd(int number, int gcd_value){
    while(gcd_value != 1){
      number /= gcd_value;
      gcd_value = gcd(number, gcd_value);
    }

    return number;
  }

  int gcd(int a, int b) {
    if(a % b == 0)
      return b;
    else
      return gcd(b, a % b);
  }