#include<fstream.h>
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[801],x,y,z,s=0,n,i;
int main(){
	f>>n;
	for(i=1;i<=n;++i);
	f>>v[i];
	//sort (v+1,v+1+r);
	for (x=1;x<=n-2;x++)
		for(y=x+1;y<=n-1;++y)
			for(z=y+1;z<=n;++z)
				if(v[x]<=v[y]+v[z]&&v[y]<=v[x]+v[z]&&v[z]<=v[x]+v[y])
					s=s+1;
				{
					g<<s<<'\n';
					g.close();
					return 0;
					}
					{z=y+1;
					while(v[x]+v[y]>=v[z])z+1;
						s=s+z;
					}
}