#include<fstream.h>
int main()
{unsigned v[801], n, a, i, j, ok, aux, k;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
f>>n;
a=0;
for (i=1; i<=n; i++) f>>v[i];
do {ok=0;
    for (i=1; i<=n-1; i++)
         if (v[i]>v[i+1]) {aux=v[i]; v[i]=v[i+1]; v[i+1]=aux; ok=1;}
    }
while (ok==1);
for (i=1; i<=n-2; i++)
		for(j=i+1; j<=n-1; j++)
			for (k=n; k>=j+1; k--)
				if (v[i]+v[j]<v[k]) break;
				else if (v[i]+v[k]>=v[j]&&v[j]+v[k]>=v[i]) a++;
			
g<<a;
f.close();
g.close();
return 0;
}