#include<stdio.h>

short v[801000],n;

int valid(int a,int b, int c)
{ if(v[a]>v[b]+v[c])return 0;
  if(v[b]>v[a]+v[c])return 0;
  if(v[c]>v[a]+v[b])return 0;

return 1;




}

int main(void){
freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);

scanf("%hd",&n);
int i,j,k,contor=0;
for(i=1; i<=n; i++)scanf("%hd",&v[i]);

for(i=1; i<=n-2; i++)
for(j=i+1; j<=n-1; j++)
for(k=j+1; k<=n; k++)
if(valid(i,j,k))contor++;

printf("%d",contor);
return 0;
}