#include <stdio.h>

int v[2001];

int main()
{
    FILE *fin,*fout;
    int n,nr,i,k,j,max,p,u,f;
    fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");
    fscanf(fin,"%d", &n);
    for (i=1;i<=n;i++)
        fscanf(fin,"%d", &v[i]);
    for (u=n;u>=0;u--) {
        max=v[0];
        p=0;
        for (i=1;i<=u;i++)
            if (v[i]>max) {
                max=v[i];
                p=i;
            }
        v[p]=v[u];
        v[u]=max;
    }
    nr=0;
    for( i=1;i<=n;i++)
        for( j=i+1;j<=n;j++){
            f=j+1;
            while(f<=n && v[i]+v[j]>=v[f] && v[i]+v[f]>=v[j] && v[j]+v[f]>=v[i]){
                f++;
                nr++;
            }
        }
    fprintf(fout,"%d", nr);
    return 0;
}