#include<cstdio>
#define InFile "nrtri.in"
#define OutFile "nrtri.out"
using namespace std;
int n,k,v[811];
int main()
{
    FILE *f=fopen(InFile,"r");
    FILE *g=fopen(OutFile ,"w");
    fscanf(f,"%d",&n);
    for(int i=1;i<=n;++i)fscanf(f,"%d",&v[i]);
     for(int i=1;i<=n;++i)
     for(int j=i+1;j<=n;++j)
     for(int g=j+1;g<=n;++g)
      if(v[i]<=v[j]+v[g]&&v[j]<=v[i]+v[g]&&v[g]<=v[i]+v[j])k++;

fprintf(g,"%d",k);
  return 0;
}