#include <stdio.h>

int v[801];

int main()
{
    int i=0,n=0,j=0,k=0,s=0;
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for (i=0; i<n; ++i)
        scanf("%d",&v[i]);
    for (i=0; i<n; ++i)
        for (j=i+1; j<n; ++j)
            for (k=j+1; k<n; ++k)
                if (v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i])
                    ++s;
    printf("%d",s);
    return 0;
}