#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
    int N;
    cin>>N;
    vector<pair<int,int>> S(N);
    for(int i=0;i<N;i++) cin>>S[i].first>>S[i].second;
    sort(S.begin(),S.end());
    int ind = 0;
    priority_queue<int,vector<int>,greater<int>> pq;
    int l = 1e18;
    for(int i=0;i<N;i++) l = min(l,S[i].first-(i+1));
    l = max(0ll,l);
    int ll = l;
    for(int i=S[0].first+l;i<S[0].first+N+l;i++){
        while(ind != N && S[ind].first <= i){
            pq.push(S[ind].second);
            ind++;
        }
        if(pq.empty() || pq.top() < i){
            cout<<0<<endl;
            return 0;
        }
        pq.pop();
    }
    for(int z=30;z>=0;z--){
        while(pq.size()) pq.pop();
        ind = 0;
        l += (1ll<<z);
        bool p = true;
        for(int i=S[0].first+l;i<S[0].first+N+l;i++){
            while(ind != N && S[ind].first <= i){
                pq.push(S[ind].second);
                ind++;
            }
            if(pq.empty() || pq.top() < i){
                p = false;
                break;
            }
            pq.pop();
        }
        if(!p) l -= (1<<z);
    }
    cout<<l-ll+1<<endl;
}