program alex;
var f:text;
    a:array[1..850]of integer;
    i,j,h,d,n:longint;
begin
assign(f,'nrtri.in');reset(f);
readln(f,n);
for i:=1 to n do
    read(f,a[i]);
close(f);
d:=0;
for i:=1 to n-2 do
    for j:=i+1 to n-1 do
        for h:=j+1 to n do
            if(a[i]+a[j]>=a[h])and(a[i]+a[h]>=a[j])and(a[h]+a[j]>=a[i]) then d:=d+1;
assign(f,'nrtri.out');rewrite(f);
writeln(f,d);
close(f);
end.