#include <stdio.h>
int main(){
int n,m,a[10000],s;
scanf("%d",&n);m=s=n;
while(s)scanf("%d",a+n-s--);
while(n--)for(s=0;s++-n;)a[s-1]>a[s]&&(a[s-1]^=a[s]^=a[s-1]^=a[s]);
while(--m)if(s=a[m]-a[m-1])n=!~n||s<n?s:n;
printf("%d",~n?n:0);
return 0;
}