#include<stdio.h>
#include<algorithm>
using namespace std;
long long a[100005],i,j,k,l,s,m,n,ans;
int main() 
{
    while (scanf("%d%d",&n,&m)!=EOF) 
    {
        ans=0;
        for (i=1;i<=n;i++)
            scanf("%d",&a[i]),a[i]%=m;
        sort(a+1,a+1+n);
        for (int i=1;i<=n;i++) 
        {
            int ll=1,rr=n,s=0;
            while (ll<=rr) 
            {
                int mid1=(ll+rr)>>1;
                if (a[i]+a[mid1]>=m) rr=mid1-1,s=mid1-1;
                else ll=mid1+1;
            }
            ll=1,rr=s;
            if (s==i) s--;
            if (s) ans=max(ans,a[i]+a[s]);
            if (s!=n) 
            {
                if (i!=n) ans=max(ans,(a[i]+a[n])%m);
                else ans=max(ans,(a[i]+a[n-1])%m);
            }
        }
        printf("%d\n",ans);
    }
}