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