#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int N = 200000;
ll a[N+5][2], b[N+5][2];
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
int n;
cin >> n;
ll res = 0;
for(int i=1; i<=2*n; i++){
int x, y;
cin >> x >> y;
if(x < 1){
res += 1 - x;
x = 1;
}
if(x > n){
res += x - n;
x = n;
}
if(y < 1){
res += 1 - y;
y = 1;
}
if(y > 2){
res += y - 2;
y = 2;
}
a[x][2 - y]++;
}
for(int i=1; i<=n; i++) b[i][0] = 1;
for(int i=1; i<=n; i++) b[i][1] = 1;
ll c0 = 0, c1 = 0;
for(int i=1; i<=n; i++){
ll k = min(a[i][0], b[i][0]);
a[i][0] -= k, b[i][0] -= k;
k = min(a[i][1], b[i][1]);
a[i][1] -= k, b[i][1] -= k;
k = max(0LL, min(c0, a[i][0]));
res += i*k;
c0 -= k, a[i][0] -= k;
k = max(0LL, min(c1, a[i][1]));
res += i*k;
c1 -= k, a[i][1] -= k;
k = max(0LL, min(c1, a[i][0]));
res += (i + 1)*k;
c1 -= k, a[i][0] -= k;
k = max(0LL, min(c0, a[i][1]));
res += (i + 1)*k;
c0 -= k, a[i][1] -= k;
if(c0 < 0 && b[i][0]){
b[i][0] = 0;
res += i;
c0++;
}
if(c1 < 0 && b[i][1]){
b[i][1] = 0;
res += i;
c1++;
}
if(a[i][0] && b[i][1]){
a[i][0]--, b[i][1] = 0;
res++;
}
if(a[i][1] && b[i][0]){
a[i][1]--, b[i][0] = 0;
res++;
}
if(c1 < 0 && b[i][0]){
b[i][0] = 0;
res += i + 1;
c1++;
}
if(c0 < 0 && b[i][1]){
b[i][1] = 0;
res += i + 1;
c0++;
}
res -= i*a[i][0];
c0 -= a[i][0];
res -= i*a[i][1];
c1 -= a[i][1];
if(b[i][0]){
res -= i;
c0++;
}
if(b[i][1]){
res -= i;
c1++;
}
}
if(c0 || c1) cout << "-1\n";
else cout << res << "\n";
return 0;
}
