#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void rd(long long &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned x){
  int s=0;
  char f[10];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(long long x){
  int s=0;
  int m=0;
  char f[20];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned long long x){
  int s=0;
  char f[21];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
int WRITER_DOUBLE_DIGIT = 15;
inline int writerDigit_double(){
  return WRITER_DOUBLE_DIGIT;
}
inline void writerDigit_double(int d){
  WRITER_DOUBLE_DIGIT = d;
}
inline void wt_L(double x){
  const int d = WRITER_DOUBLE_DIGIT;
  int k;
  int r;
  double v;
  if(x!=x || (x==x+1 && x==2*x)){
    my_putchar_unlocked('E');
    my_putchar_unlocked('r');
    my_putchar_unlocked('r');
    return;
  }
  if(x < 0){
    my_putchar_unlocked('-');
    x = -x;
  }
  x += 0.5 * pow(0.1, d);
  r = 0;
  v = 1;
  while(x >= 10*v){
    v *= 10;
    r++;
  }
  while(r >= 0){
    r--;
    k = floor(x / v);
    if(k >= 10){
      k = 9;
    }
    if(k <= -1){
      k = 0;
    }
    x -= k * v;
    v *= 0.1;
    my_putchar_unlocked(k + '0');
  }
  if(d > 0){
    my_putchar_unlocked('.');
    v = 1;
    for(r=(0);r<(d);r++){
      v *= 0.1;
      k = floor(x / v);
      if(k >= 10){
        k = 9;
      }
      if(k <= -1){
        k = 0;
      }
      x -= k * v;
      my_putchar_unlocked(k + '0');
    }
  }
}
inline void wt_L(const char c[]){
  int i=0;
  for(i=0;c[i]!='\0';i++){
    my_putchar_unlocked(c[i]);
  }
}
inline void wt_L(string &x){
  int i=0;
  for(i=0;x[i]!='\0';i++){
    my_putchar_unlocked(x[i]);
  }
}
int N;
long long A[100000];
long long B[100000];
long long sa;
long long sb;
long long d;
long long p;
int main(){
  int i;
  rd(N);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(N);Lj4PdHRW++){
      rd(A[Lj4PdHRW]);
    }
  }
  {
    int e98WHCEY;
    for(e98WHCEY=(0);e98WHCEY<(N);e98WHCEY++){
      rd(B[e98WHCEY]);
    }
  }
  {
    int FmcKpFmN;
    long long xr20shxY;
    if(N==0){
      xr20shxY = 0;
    }
    else{
      xr20shxY = A[0];
      for(FmcKpFmN=(1);FmcKpFmN<(N);FmcKpFmN++){
        xr20shxY += A[FmcKpFmN];
      }
    }
    sa =xr20shxY;
  }
  {
    int KrdatlYV;
    long long ao_dF3pO;
    if(N==0){
      ao_dF3pO = 0;
    }
    else{
      ao_dF3pO = B[0];
      for(KrdatlYV=(1);KrdatlYV<(N);KrdatlYV++){
        ao_dF3pO += B[KrdatlYV];
      }
    }
    sb =ao_dF3pO;
  }
  if(N==2){
    if(sa != sb){
      wt_L(-1);
      wt_L('\n');
      return 0;
    }
    wt_L(abs(A[0]-B[0]));
    wt_L('\n');
    return 0;
  }
  d = sa - sb;
  if(d < 0 || d % (N-2)){
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  d /= N-2;
  for(i=(0);i<(N);i++){
    A[i] -= d;
  }
  for(i=(0);i<(N);i++){
    if(B[i] - A[i] < 0 || (B[i] - A[i])%2){
      wt_L(-1);
      wt_L('\n');
      return 0;
    }
    p += (B[i] - A[i]) / 2;
  }
  if(p != d){
    wt_L(-1);
    wt_L('\n');
    return 0;
  }
  wt_L(d);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200509-1

// --- original code ---
// int N; ll A[1d5], B[1d5];
// ll sa, sb, d, p;
// {
//   rd(N,A(N),B(N));
//   sa = sum(A(N));
//   sb = sum(B(N));
//   if(N==2){
//     if(sa != sb) wt(-1), return 0;
//     wt(abs(A[0]-B[0]));
//     return 0;
//   }
// 
//   d = sa - sb;
//   if(d < 0 || d % (N-2)) wt(-1), return 0;
//   d /= N-2;
// 
//   rep(i,N) A[i] -= d;
//   rep(i,N){
//     if(B[i] - A[i] < 0 || (B[i] - A[i])%2) wt(-1), return 0;
//     p += (B[i] - A[i]) / 2;
//   }
//   if(p != d) wt(-1), return 0;
//   wt(d);
// }