#include <cstdio>
#include <algorithm>
using namespace std;

FILE*f=fopen("nrtri.in","r");
FILE*g=fopen("nrtri.out","w");

int n,v[801],i,j,p,s=0,aux,a[30001];

int main()
{fscanf(f,"%d",&n);
for(i=1;i<=n;i++)
fscanf(f,"%d",&v[i]);

sort(v+1,v+n+1);

for(i=1;i<=n-2;i++)
{for(j=i+1;j<=n-1;j++)
{for(p=j+1;p<=n;p++)
{if(v[i]+v[j]>=v[p])
	s++;
}
}
}

fprintf(g,"%d",s);

    return 0;
}