#include<stdio.h>
#include<algorithm>
using namespace std;
int x[800],a,i,j,n,st,dr,gasit,mij,g,k;
bool cmp(int a,int b)
{
	return a>=b;
}
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%d",&x[i]);
	}
	sort(x,x+n,cmp);
	for(i=0;i<n-2;i++)
	{
		for(j=i+1;j<n-1;j++)
		{
			for(k=j+1;k<n;k++)
			{
				
				if(x[i]<=x[j]+x[k])
					
				{
					g++;
				}
				else break;
			}
		}
	}
				
				printf("%d",g);
				return 0;
}
				
				/*
				for(a=1;a<=x[i]+x[j];a++)
				{
					st=j+1;
					dr=n-1;
					gasit=0;
					while(st<=dr)
					{
						mij=(st+dr)/2;
						if(x[mij]==a)
						{
							gasit=1;
							g++;
							break;
						}
						else
						{
							if(x[mij]<a)
							{
								st=mij+1;
							}
							else
							{
								dr=mij-1;
							}
						}
					}
				}
			}
		}
	}
	printf("%d",g);
    return 0;
}
*/