#include<cstdio>
#include<algorithm>
int n,i,j,l,nr,a[802],ls,ld,ok,x;
using namespace std;
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    sort(a+1,a+n+1);
    for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
                ls=j+1;
                ld=n;
            while(1)
            {
                ok=0;
                while(ls<=ld)
                {
                    l=(ls+ld)/2;
                    if(a[i]+a[j]>=a[l]&&a[i]+a[l]>=a[j]&&a[j]+a[l]>=a[i]&&l!=x){ok=1;x=l;break;}
                    else
                    {
                        if(a[i]+a[j]<a[l])ld=l-1;
                        else ls=l+1;
                    }
                }
                if(ok==1){nr++;}
                else break;
            }
        }
    }
    printf("%d",nr);
    return 0;
}
    /*for(i=1;i<=n-2;i++)
    {
        for(j=i+1;j<=n-1;j++)
        {
            for(l=j+1;l<=n;l++)
            {
                if(a[i]+a[j]>=a[l]&&a[i]+a[l]>=a[j]&&a[j]+a[l]>=a[i])nr++;
            }
        }
    }
    printf("%d",nr);
    return 0;
}
*/