#include <cstdio>
#include <algorithm>
using namespace std;FILE*fin=fopen("nrtri.in","r");FILE*fout=fopen("nrtri.out","w");int a,b,i,j,k,n,m,v[802],rasp;int main(){fscanf(fin,"%d",&n);for (i=1;i<=n;i++) fscanf(fin,"%d",&v[i]);sort(v+1,v+n+1);for (i=1;i<n-1;i++)for (j=i+1;j<=n-1;j++)rasp+=std::distance(lower_bound(v+j+1,v+n+1,v[i]-v[j]),upper_bound(v+j+1,v+n+1,v[j]+v[i]));fprintf(fout,"%d\n",rasp);return 0;}