#include <bits/stdc++.h>
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=1050000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a,bool upp=0){if(a) cout<<(upp?"YES\n":"Yes\n"); else cout<<(upp?"NO\n":"No\n");}
template<class T> void vec_out(vector<T> &p,int ty=0){
if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}


void solve();
// oddloop
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int t=1;
    //cin>>t;
    rep(i,0,t) solve();
}

void solve(){
    int N;
    cin>>N;
    struct F{
        int l;
        int r;
    };
    vector<F> p(N);
    int tmp=-INF;
    rep(i,0,N) cin>>p[i].l>>p[i].r,p[i].l--;
    sort(all(p),[&](F a,F b){
        return a.l<b.l;
    });
    rep(i,0,N) chmax(tmp,p[i].l-i);
    rep(i,0,N) p[i].l-=tmp,p[i].r-=tmp;
    auto f=[&](int c) -> bool {
        map<int,int> m;
        auto add=[&](int a,int b) -> void {
            m[a]+=b;
            if(m[a]==0) m.erase(a);
        };
        int ind=0;
        rep(i,c,N+c){
            while(ind<N&&p[ind].l<=i) add(p[ind].r,1),ind++;
            //cout<<m.size()<<endl;
            if(m.empty()||(*m.begin()).first<=i) return false;
            add((*m.begin()).first,-1);
        }
        return true;
    };
    //for(auto x:p) cout<<x.l<<" "<<x.r<<endl;
    if(!f(0)){
        cout<<"0\n";
        return;
    }
    int L=0,R=INF;
    while(R-L>1){
        int M=(L+R)/2;
        if(f(M)) L=M;
        else R=M;
        //cout<<L<<" "<<R<<endl;
    }
    cout<<R<<"\n";
}