#include <bits/stdc++.h>
using namespace std;
#define vodichc2 ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define fr(i,a,b) for(long long i=a;i<=b;i++)
#define frd(i,a,b) for(long long i=a;i>=b;i--)
#define openfile if(fopen("Data.inp","r")) {freopen("Data.inp", "r", stdin); freopen("Data.out", "w", stdout);}
ll n,a[200005];
void doc()
{
cin >> n;
fr(i,1,n) cin >> a[i];
sort(a+1,a+n+1);
}
void xuly()
{
ll res=0;
// fr(i,1,n)
// fr(j,i+1,n)
// {
// res=max(a[j]%a[i],res);
// }
// cout << res;
a[n+1]=1e9;
fr(i,1,n)
{
for(ll t=a[i];t<=a[n]+a[i];t+=a[i])
{
ll j=lower_bound(a+1,a+n+2,t)-a;
j--;
if(j>0)
{
if(a[j]>a[i]) res=max(res,a[j]%a[i]);
}
}
}
cout << res;
}
signed main()
{
vodichc2
openfile
doc();
xuly();
}
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*/
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