type matrice=array[1..2,1..1000] of longint;
     vector=array[1..1000] of real;
var a:matrice;
    n,x,y,i,j,t,k:longint;
    f,g:text;
    v:vector;
begin
       assign(f,'trapez.in');
       reset(f);
       readln(f,n);
           for j:=1 to n do
             begin
           readln(f,x,y);
           a[1,j]:=x;
           a[2,j]:=y;
              end;
      close(f);
                k:=0;
           for i:=1 to n-1 do
             for j:=i+1 to n do
                begin
              k:=k+1;
           v[k]:=(a[2,j]-a[2,i])/(1+(a[1,j]-a[1,i]));
                 end;
               t:=0;
           for i:=1 to k-1 do
              for j:=i+1 to k do
            if v[i]=v[j] then t:=t+1;
            assign(g,'trapez.out');
            rewrite(g);
            write(g,t);
            close(g);

end.