#include<cstdio>
#include<algorithm>
using namespace std;
int v[805
]
int main ()
{
   freopen("nrtri.in","r",stdin);
   freopen("nrtri.out","w",stdout);
   int i,n,a,b,c,k;
    scanf("%d",&n);
    k=0;
    for(i=0;i<n;i++) scanf("%d",&v[i]);
    sort(v,v+n);
    for(a=0;a<n-2;a++)
        for(b=a+1;b<n-1;b++);
            for(c=b+1;c<n;c++)
                if(v[c]<=v[a]+v[b])
                    k++;
                    else break;
    printf("%d",k);
    return 0;

}