#include <bits/stdc++.h>
using namespace std;
int main(){
cin.tie(0);
ios::sync_with_stdio(0);
int n;
cin >> n;
vector<pair<int, int>> strings(n);
for(int i = 0; i < n; i++){
cin >> strings[i].first >> strings[i].second;
}
sort(strings.begin(), strings.end());
map<int, int> freq;
for(int i = 0; i < n; i++){
int s = strings[i].first;
int e = strings[i].second;
int circle_dist = min(abs(s - e), (2 * n) - abs(s - e));
freq[circle_dist]++;
}
for(auto e : freq){
int amount = e.second;
if(amount != 2){
cout << 2 << "\n";
return 0;
}
}
cout << 0 << "\n";
}
