#include<cstdio>

 #include<cstring>

 #include<algorithm>

 using namespace std;

 const int N=+;

 struct E {

     int v,nxt;

 } e[N*N];

 int n,hd[N],ne;

 void init() {memset(hd,-,sizeof hd); ne=;}

 void addedge(int u,int v) {e[ne]= {v,hd[u]},hd[u]=ne++;}

 int dfn[N],low[N],scc[N],sta[N],nscc,nsta,tot;

 void dfs(int u) {

     dfn[u]=low[u]=++tot;

     sta[nsta++]=u;

     for(int i=hd[u]; ~i; i=e[i].nxt) {

         int v=e[i].v;

         if(!dfn[v])dfs(v),low[u]=min(low[u],low[v]);

         else if(!scc[v])low[u]=min(low[u],dfn[v]);

     }

     if(low[u]==dfn[u]) {

         nscc++;

         for(; !scc[u]; scc[sta[--nsta]]=nscc);

     }

 }

 void getscc() {

     memset(dfn,,sizeof dfn);

     memset(scc,,sizeof scc);

     tot=nscc=nsta=;

     for(int i=; i<n*; ++i)if(!dfn[i])dfs(i);

 }

 int x[N],y[N];

 int p1(int x) {return x<<;}

 int p2(int x) {return x<<|;}

 bool ok(int k) {

     init();

     for(int i=; i<n; ++i)

         for(int j=i+; j<n; ++j) {

             if(abs(x[i]-x[j])<k)addedge(p1(i),p2(j)),addedge(p1(j),p2(i));

             if(abs(x[i]-y[j])<k)addedge(p1(i),p1(j)),addedge(p2(j),p2(i));

             if(abs(y[i]-x[j])<k)addedge(p2(i),p2(j)),addedge(p1(j),p1(i));

             if(abs(y[i]-y[j])<k)addedge(p2(i),p1(j)),addedge(p2(j),p1(i));

         }

     getscc();

     for(int i=; i<n; ++i)if(scc[p1(i)]==scc[p2(i)])return false;

     return true;

 }

 int bi(int l,int r) {for(int mid; l<r; mid=(l+r+)>>,ok(mid)?l=mid:r=mid-); return l;}

 int main() {

     while(scanf("%d",&n)==) {

         for(int i=; i<n; ++i)scanf("%d%d",&x[i],&y[i]);

         printf("%d\n",bi(,(int)1e7));

     }

     return ;

 }