//#define _GLIBCXX_DEBUG

#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = int;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e9;
using P = pair<ll, ll>;
template<typename T1, typename T2>
bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>
bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>
void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>
void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++)
{for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>
void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];
for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>
vector<vector<T>>vec(ll x, ll y, T w){
  vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};
vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>
vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v(ts...))>(a,make_v(ts...));
}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2>&p){
  return os << p.first << " " << p.second;
}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
struct RangeGraph{
  vector<vector<ll>>g;
  ll n,sz;
  ll cnt;
  RangeGraph(ll n,ll m):n(n){
    sz=1;
    cnt=0;
    while(sz<n)sz <<= 1;
    g.assign(3*sz+m,vector<ll>());
    for(ll i=1;i<sz;i++){
      g[i].EB(2*i);
      g[i].EB(2*i+1);
      if(2*i<sz){
        g[2*i+2*sz].EB(i+2*sz);
        g[2*i+1+2*sz].EB(i+2*sz);
      }
      else{
        g[2*i].EB(i+2*sz);
        g[2*i+1].EB(i+2*sz);
      }
    }
  }
  void add_edge(ll l1,ll r1,ll l2,ll r2){//[l1,r1)->[l2,r2)
    if(l1>=r1||l2>=r2)return;
    if(l1+1==r1&&l2+1==r2){
      g[l1+sz].EB(l2+sz);
    }
    else if(l1+1==r1){
      auto v=range(l2,r2);
      v=range(l2,r2);
      for(auto z:v)g[l1+sz].EB(z);
    }
    else if(l2+1==r2){
      auto v=range(l1,r1);
      for(auto z:v){
        if(z<sz)g[z+2*sz].EB(l2+sz);
        else g[z].EB(l2+sz);
      }
    }
    else{
      auto v=range(l1,r1);
      ll via=3*sz+cnt;
      for(auto z:v){
        if(z<sz)g[z+2*sz].EB(via);
        else g[z].EB(via);
      }
      v=range(l2,r2);
      for(auto z:v)g[via].EB(z);
      cnt++;
    }
  }
  vector<ll>range(ll l,ll r){
    vector<ll>ret;
    l+=sz,r+=sz;
    while(l!=r){
      if(l&1)ret.PB(l++);
      if(r&1)ret.PB(--r);
      l>>=1,r>>=1;
    }
    return ret;
  };
  ll add(){
    return sz;
  }
};

struct SCC{
  ll n;
  vector<vector<ll>>G,Gr;
  vector<ll>index;//各ノードが属する強連結成分の番号
  vector<ll>ret;//dfsに使う
  SCC(vector<vector<ll>>g):G(g),n(g.size()){
    index.assign(n,-1LL);
    build();
  }
  void build(){
    Gr.assign(n,vector<ll>());
    for(ll i=0;i<n;i++){
      for(ll j=0;j<G[i].size();j++){
        Gr[G[i][j]].push_back(i);
      }
    }
    for(ll i=0;i<n;i++)if(index[i]==-1)dfs1(i);
    fill(ALL(index),-1);
    ll cnt=0;
    reverse(ALL(ret));
    for(ll i=0;i<n;i++){
      if(index[ret[i]]==-1){
        dfs2(ret[i],cnt);
        cnt++;
      }
    }
  }
  void dfs1(ll k){
    index[k]=1;
    for(ll i=0;i<G[k].size();i++){
      if(index[G[k][i]]==-1)dfs1(G[k][i]);
    }
    ret.push_back(k);
  }
  void dfs2(ll k, ll idx){
    index[k]=idx;
    for(ll i=0;i<Gr[k].size();i++){
      if(index[Gr[k][i]]==-1)dfs2(Gr[k][i],idx);
    }
  }
  vector<vector<ll>>edges;
  void build_edges(){
    edges.assign(*max_element(ALL(index))+1,vector<ll>());
    for(ll i=0;i<n;i++){
      for(ll j=0;j<G[i].size();j++){
        if(index[i]!=index[G[i][j]]){
          edges[index[i]].push_back(index[G[i][j]]);
        }
      }
    }
  }
  vector<ll>output(){return index;};
};

int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll n;cin>>n;
  vector<ll>x(n),y(n);
  rep(i,0,n)cin>>x[i]>>y[i];
  vector<P>v;
  rep(i,0,n)v.EB(x[i],i),v.EB(y[i],i);
  sort(ALL(v));
  vector<vector<ll>>t(n);
  rep(i,0,2*n)t[v[i].se].PB(i);
  ll ok=0,ng=(ll)1e9;
  //debug(v,2*n);
  //debug(t,n,2);
  while(abs(ok-ng)>=2){
    ll mid=(ok+ng)/2;
    RangeGraph rg(4*n,0);
    rep(i,0,2*n){
      ll idx=lower_bound(ALL(v),MP(v[i].fi+mid,-1))-v.begin();
      rg.add_edge(i,i+1,2*n+i+1,2*n+idx);
      rg.add_edge(i+1,idx,i+2*n,i+1+2*n);
    }
    ll add=rg.add();
    rep(i,0,n){
      rg.g[t[i][1]+2*n+add].EB(t[i][0]+add);
      rg.g[t[i][0]+2*n+add].EB(t[i][1]+add);
    }
    SCC scc(rg.g);
    bool sw=true;
    rep(i,0,2*n){
      if(scc.index[i+add]==scc.index[i+2*n+add]){
        sw=false;
      }
    }
    if(sw)ok=mid;
    else ng=mid;
  }
  cout<<ok<<endl;
  return 0;
}


Measured memory_bytes: 64096