program p1;
var f,g:text;
    x:array[1..800] of longint;
    i,n,a,b,c,nr,j,l:longint;
begin
     assign(f,'nrtri.in');reset(f);
     assign(g,'nrtri.out');rewrite(g);
     read(f,n);
     for i:=1 to n do read(f,x[i]);
     nr:=0;
     for i:=1 to n-2 do
         for j:=i+1 to n-1 do
             for l:=j+1 to n do
                 if (x[i]+x[j]>=x[l])and(x[i]+x[l]>=x[j])and(x[j]+x[l]>=x[i]) then nr:=nr+1;
     writeln(g,nr);
     close(f);
     close(g);
end.