#include<cstdio>#include<cstring>#include<cctype>#include<algorithm>using namespace std;#define rep(i,s,t) for(int i=s;i<=t;i++)#define dwn(i,s,t) for(int i=s;i>=t;i--)#define clr(x,c) memset(x,c,sizeof(x))int read(){	int x=0;char c=getchar();	while(!isdigit(c)) c=getchar();	while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();	return x;} const int nmax=2e5+5;int a[nmax];int main(){	int n=read();	rep(i,1,n) a[i]=read();	sort(a+1,a+n+1);	int ans=0,tp;	rep(i,1,n-1){		for(int j=a[i]+a[i];j<=a[n]*2;j+=a[i]){			tp=lower_bound(a+1,a+n+1,j)-a-1;ans=max(ans,a[tp]%a[i]);		}	} 	printf("%d\n",ans);	return 0; }