#include <iostream>
#include <cstdio>
#include<algorithm>
using namespace std;

int v[802];

int main()
{
    int n,i,j,nrtri=0,k=0;
    FILE*fin,*fout;
    fin=fopen("nrtri.in","r");
    fscanf(fin,"%d",&n);
    for(i=1;i<=n;i++){
        fscanf(fin,"%d",&v[i]);
    }
    fclose(fin);
    sort(v+1,v+n+1);
    for(i=1;i<=n;i++){
        k=i+2;
        for(j=i+1;j<=n;j++){
            while(k<=n && v[i]+v[j]>=v[k])
              k++;
            if(j+1<=k+1)
              nrtri+=k-j-1;
        }
    }
    fout=fopen("nrtri.out","w");
    fprintf(fout,"%d",nrtri);
    fclose(fout);
    return 0;
}