#include<iostream>
#include<cstdio>
#include<stack>
#include<algorithm>
#include<cstring>
using namespace std;

int v[100005];
int n,x,y,tot=0,h[100005];
int scc[100005],dfn[100005],low[100005],C,cnt;
bool vis[100005];
struct Edge{
	int x,next;
}e[5000000];
pair<int,int> a[20005];
stack<int> s;

inline void add_edge(int x,int y){
	e[++tot].x=y;
	e[tot].next=h[x],h[x]=tot;
}

void tarjan(int x){
	dfn[x]=low[x]=++cnt;
	s.push(x),vis[x]=true;
	for(int i=h[x];~i;i=e[i].next){
		if(!dfn[e[i].x]){
			tarjan(e[i].x),low[x]=min(low[x],low[e[i].x]);
		}else if(vis[e[i].x]){
			low[x]=min(low[x],dfn[e[i].x]);
		}   
	}
	if(dfn[x]==low[x]){
		C++;
		int tmp;
		for(;;){
			tmp=s.top();
			vis[tmp]=false,scc[tmp]=C;
			s.pop();
			if(tmp==x)break;
		}
	}
}

void build(int o,int l,int r){
	if(r-l==1){
		add_edge(o+n*2,a[l].second^1);
		return;
	}
	add_edge(o+n*2,(o<<1)+n*2);
	add_edge(o+n*2,(o<<1|1)+n*2);
	int mid=l+r>>1;
	build(o<<1,l,mid),build(o<<1|1,mid,r);
}

void link(int o,int l,int r,int x,int y,int a){
	if(l>=x&&r<=y){
		add_edge(a,o+n*2);
		return;
	}
	int mid=l+r>>1;
	if(x<mid)link(o<<1,l,mid,x,y,a);
	if(y>mid)link(o<<1|1,mid,r,x,y,a);
}

inline pair<int,int> get(int x,int len){
	int l=0,r=x;
	pair<int,int> ans;
	while(l<r){
		int mid=l+r>>1;
		if(a[x].first-a[mid].first<len)r=mid;
		else l=mid+1;
	}
	ans.first=l;
	l=x,r=n*2-1;
	while(l<r){
		int mid=l+r+1>>1;
		if(a[mid].first-a[x].first<len)l=mid;
		else r=mid-1;
	}
	ans.second=l;
	return ans;
}

inline bool check(int d){
	memset(scc,0,sizeof(scc));
	memset(dfn,0,sizeof(dfn));
	memset(low,0,sizeof(low));
	memset(h,-1,sizeof(h)),tot=0;
	build(1,0,n*2);
	for(int i=0;i<n*2;i++){
		int id=a[i].second;
		pair<int,int> x=get(i,d);
		if(i<x.second)link(1,0,n*2,i+1,x.second+1,id);
		if(x.first<i)link(1,0,n*2,x.first,i,id);
	}
	C=cnt=0;
	for(int i=0;i<n*2;i++)if(!dfn[i])tarjan(i);
	for(int i=0;i<n*2;i++)
		if(scc[a[i].second]==scc[a[i].second^1])return false;
	return true;
}

int main(){
	scanf("%d",&n);
	for(int i=0;i<n;i++){
		scanf("%d%d",&x,&y);
		a[2*i+1]=make_pair(x,2*i+1);
		a[2*i]=make_pair(y,2*i);
	}
	sort(a,a+n*2);
	int l=0,r=1000000000;
	while(l<r){
		int mid=l+r+1>>1;
		if(check(mid))l=mid;
		else r=mid-1;
	}
	printf("%d",l);
}