#include<fstream.h>
int main()
{unsigned v[801], n, a, i, j, k;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n;
a=0;
if (n<3) g<<0;
else 
{for (i=1; i<=n; i++) f>>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 (v[i]+v[j]>=v[k]&&v[i]+v[k]>=v[j]&&v[j]+v[k]>=v[i]) a++;
g<<a;
}
f.close();
g.close();
return 0;
}