#include<stdio.h>
#include<algorithm>
using namespace std;
int N,a[801],s=0;
int caut(int x, int y)
{
    int ret=-1;
    int st=y;
    int dr=N;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(a[mij]>a[x]+a[y])
            dr=mij-1;
        else
        {
            ret=mij;
            st=mij+1;
        }
    }
    return ret;
}
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&N);
    for(int i=1;i<=N;++i)
        scanf("%d",&a[i]);
    sort(a+1,a+N+1);
    for(int i=1;i<=N-2;++i)
        for(int j=i+1;j<=N-1;++j)
            s=s+caut(i,j)-j;
    printf("%d",s);
    return 0;
}