1 #include<bits/stdc++.h>
  2 using namespace std;
  3 const int N=1e6+10;
  4 int head[N],col[N],dfn[N],low[N],s[N],in[N],xx[N],yy[N],pos[N];
  5 int n,c,rt,ans,cnt,tmp,num,pre,top;
  6 struct tree{
  7     int l,r;
  8 }t[N<<2];
  9 struct edge{
 10     int to,nex;
 11 }e[N<<1];
 12 struct node{
 13     int x,y;
 14     bool operator <(const node &b)const{
 15         return x<b.x;
 16     }
 17 }a[N];
 18 void add(int x,int y)
 19 {
 20     e[++cnt].to=y;e[cnt].nex=head[x];head[x]=cnt;
 21 }
 22 void build(int &x,int l,int r)
 23 {
 24     if(l==r){
 25         x=(a[l].y<=n)?a[l].y+n:a[l].y-n;
 26         pos[a[l].y]=l;return;
 27     }x=++num;
 28     int mid=l+r>>1;
 29     build(t[x].l,l,mid);build(t[x].r,mid+1,r);
 30     add(x,t[x].l);add(x,t[x].r);
 31     return;
 32 }
 33 void change(int x,int l,int r,int L,int R,int p)
 34 {
 35     if(L>R)return;
 36     if(l==L&&r==R)
 37     {
 38         add(p,x);return;
 39     }
 40     int mid=l+r>>1;
 41     if(mid>=R)change(t[x].l,l,mid,L,R,p);
 42     else if(L>mid)change(t[x].r,mid+1,r,L,R,p);
 43     else change(t[x].l,l,mid,L,mid,p),change(t[x].r,mid+1,r,mid+1,R,p);
 44     return;
 45 }
 46 void dfs(int x)
 47 {
 48     dfn[x]=low[x]=++tmp;
 49     s[++top]=x;in[x]=1;
 50     for(int i=head[x];i;i=e[i].nex)
 51     {
 52         int y=e[i].to;
 53         if(!dfn[y])
 54         {
 55             dfs(y);
 56             low[x]=min(low[x],low[y]);
 57         }
 58         else if(in[y])low[x]=min(low[x],dfn[y]);
 59     }
 60     if(low[x]==dfn[x])
 61     {
 62         c++;int a=-1;
 63         do{
 64             a=s[top--];
 65             in[a]=0;
 66             col[a]=c;
 67         }while(a!=x);
 68     }
 69     return;
 70 }
 71 void init()
 72 {
 73     memset(dfn,0,sizeof(dfn));
 74     memset(low,0,sizeof(low));
 75     memset(col,0,sizeof(col));
 76     tmp=c=0;
 77     return;
 78 }
 79 bool judge(int x)
 80 {
 81     init();
 82     for(int i=1;i<=n*2;++i)head[i]=0;cnt=pre;
 83     for(int i=1;i<=n;++i)
 84     {
 85         int AL=lower_bound(a+1,a+1+2*n,(node){xx[i]-x+1,0})-a;
 86         int AR=upper_bound(a+1,a+1+2*n,(node){xx[i]+x-1,0})-a-1;
 87         if(AL<=AR)change(rt,1,n*2,AL,pos[i]-1,i),change(rt,1,n*2,pos[i]+1,AR,i);
 88         int BL=lower_bound(a+1,a+1+2*n,(node){yy[i]-x+1,0})-a;
 89         int BR=upper_bound(a+1,a+1+2*n,(node){yy[i]+x-1,0})-a-1;
 90         if(BL<=BR)change(rt,1,n*2,BL,pos[i+n]-1,i+n),change(rt,1,n*2,pos[i+n]+1,BR,i+n);
 91     }
 92     for(int i=1;i<=num;++i)
 93     if(!dfn[i])dfs(i);
 94     for(int i=1;i<=n;++i)
 95     if(col[i]==col[i+n])return 0;
 96     return 1;
 97 }
 98 int main()
 99 {
100     scanf("%d",&n);
101     for(int i=1;i<=n;++i)
102     {
103         scanf("%d%d",&xx[i],&yy[i]);
104         a[i*2-1].x=xx[i];a[i*2].x=yy[i];
105         a[i*2-1].y=i;a[i*2].y=i+n;
106     }num=n*2;
107     sort(a+1,a+1+n*2);
108     build(rt,1,n*2);
109     int l=0,r=1e9;pre=cnt;
110     while(l<=r)
111     {
112         int mid=l+r>>1;
113         if(judge(mid))ans=mid,l=mid+1;
114         else r=mid-1;
115     }
116     printf("%d\n",ans);
117     return 0;
118 }