#include <stdio.h>
int v[801];
int main(){
    int n,i,j,l,s;
    FILE *fin,*fout;
    fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");
    fscanf(fin,"%d",&n);
    if(n==1||n==2)
        fprintf(fout,"0");
    else {
    for(i=0;i<n;i++)
        fscanf(fin,"%d",&v[i]);
    s=0;
    for(i=0;i<n-2;i++){
        for(j=i+1;j<n-1;j++){
            for(l=j+1;l<n;l++){
                if(v[i]>=v[j]){
                    if(v[l]>=v[i]){
                        if(v[l]<=v[i]+v[j])
                            s++;
                    }else if(v[i]<=v[l]+v[j])
                            s++;
                }else {if(v[l]>=v[j]){
                          if(v[l]<=v[i]+v[j])
                             s++;
                       }else if(v[j]<=v[l]+v[i])
                                s++;
                }
            }
        }
    }
    fprintf(fout,"%d",s);
    }
    return 0;
}