program p1;
var a,b:array[0..801] of integer;
    f,g:text;
    i,n,j,k,u,aux,sol:longint;
begin
assign(f,'nrtri.in');reset(F);
assign(g,'nrtri.out');rewrite(G);
readln(f,n);
for i:=1 to n do begin
                read(f,a[i]);
                 end;
for i:=1 to n-1 do
        for j:=i+1 to n do
                if a[i]>a[j] then begin
                        aux:=a[i];
                        a[i]:=a[j];
                        a[j]:=aux;
                                end;
for i:=1 to n do
         for j:=i+1 to n do
                for k:=j+1 to n do
                        if a[i]+a[j]>=a[k] then inc(sol);
writeln(g,sol);
close(F);
close(G);
end.