#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define mp make_pair
#define si(x) int(x.size())
const int mod=998244353,MAX=300005;
const ll INF=1LL<<60;

int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll N;cin>>N;
    vector<ll> L(N),R(N);
    vector<pair<ll,ll>> S(N);
    for(int i=0;i<N;i++){
        ll a,b;cin>>a>>b;
        L[i]=a;
        R[i]=b;
        S[i]=mp(a,b);
    }
    sort(all(L));
    sort(all(R));
    reverse(all(R));
    ll le=-INF,ri=INF;
    
    for(int i=0;i<N;i++){
        chmax(le,L[i]-(i+1));
        chmin(ri,R[i]-(N-i));
    }
    
    if(le<=ri){
        for(int i=0;i<N;i++){
            S[i].fi-=le;
            S[i].se-=le;
            chmax(S[i].fi,1LL);
            chmin(S[i].fi,N);
            chmax(S[i].se,1LL);
            chmin(S[i].se,N);
        }
        
        sort(all(S));
        priority_queue<ll,vector<ll>,greater<ll>> PQ;
        
        int j=0;
        for(int i=1;i<=N;i++){
            while(j<N&&S[j].fi==i){
                PQ.push(S[j].se);j++;
            }
            if(si(PQ)==0){
                cout<<0<<"\n";
                return 0;
            }
            int x=PQ.top();PQ.pop();
            if(i>x){
                cout<<0<<"\n";
                return 0;
            }
        }
    }
    cout<<max(0LL,ri-le+1)<<endl;
        
}