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