a[1<<17],x,s,n;c(int*a,int*b){x=*a-*b;}main(m){for(;~scanf("%d",a-m);m--);for(qsort(a,-m,4,c);++m;n=s&&!n|s<n?s:n)s=a[-m]-a[~m];s=!printf("%d",n);}