program p1;
var a,b:array[0..1000] of longint;
    panta:array[0..1000000] of real;
    f,g:text;
    b1,b2:array[0..1 shl 17 ] of char;
    i,n,j,k,u,aux,sol:longint;
    aux1:real;
begin
assign(f,'trapez.in');reset(F);
assign(g,'trapez.out');rewrite(G);
readln(f,n);
for i:=1 to  n do begin
         readln(f,a[i],b[i]);
         if i>2 then
                for j:=1 to i-1 do  begin
                         inc(U);
                         panta[u]:=((b[i]-b[j])/(a[i]-a[j]));
                                end;
                end;
for i:=1 to u-1 do
        for j:=i+1 to u do
                if panta[i]<panta[j] then begin
                                      aux1:=panta[i];
                                      panta[i]:=panta[j];
                                      panta[j]:=aux1;
                                         end;
for i:=1 to u do
         if panta[i]=panta[i+1] then inc(sol);
writeln(G,sol);
close(F);
close(G);
end.