C++ :

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

long long b[50009];
long long ans = 9999999999;
int w,t,i,n,s = 1;
int v[50009];

struct node {
	long long x;
	long long y;
}a[50009],p[50009];

bool cmp(node k,node z) {
	return k.x < z.x;
}

int main() {
	scanf("%d",&n);
	for (i = 1; i <= n; i++) {
		scanf("%lld %lld",&a[i].x,&a[i].y);
 		b[i] = a[i].y;
	}
 	sort(a+1,a+n+1,cmp);
 	
	sort(b+1,b+n+1);
	int num = unique(b+1,b+n+1) - b - 1;
 	for (i = 1; i <= n; i++) a[i].y = lower_bound(b+1,b+num+1,a[i].y) - b;
 	
 	t = w = i = 1 ;
 	p[t].x = a[1].x; p[t].y = a[1].y;
 	v[p[t].y]++;
 	
 	for (int i = 2; i <= n; i++) {
		w++, p[w].x = a[i].x, v[a[i].y]++, p[w].y = a[i].y;
		
		if (v[p[w].y] == 1) s++;
 		
 		while (v[p[t].y] > 1) {
			v[p[t].y]--,t++;
		}
 		
 		if (s == num) {
 			long long L = p[w].x - p[t].x; ans = min(ans,L);
		}
	}
	
	printf("%lld",ans);
	
	return 0;   
}