var f1,f2:text;
    i,j,n,g,nr:longint;
    x,y:array[1..1000000] of longint;
    x1,x2:int64;
    xg,yg:array[1..1000000] of longint;
begin
        assign(f1,'trapez.in');
        reset(f1);
        assign(f2,'trapez.out');
        rewrite(f2);
        read(f1,n);
        for i:=1 to n do
                read(f1,x[i],y[i]);
        g:=0;
        for i:=1 to n-1 do
                for j:=i+1 to n do
                begin
                        inc(g);
                        xg[g]:=abs(x[i]-x[j]);
                        yg[g]:=abs(y[i]-y[j]);
                end;
        for i:=1 to g-1 do
                for j:=i+1 to g do
                begin
                        x1:=xg[i]*yg[j];
                        x2:=xg[j]*yg[i];
                        if x1=x2 then inc(nr);
                end;
        writeln(f2,nr);
        close(f1);
        close(f2);
end.