program oken;
uses crt;
var a,b,c,d,dem: longint;
tbc: real;
begin
clrscr;
write('Nhap 4 so a, b, c, d: '); readln(a,b,c,d);
tbc:=0; dem:=0;
if (a mod 2=1) then
begin
tbc:=a;
dem:=dem+1;
end;
if (b mod 2=1) then
begin
tbc:=tbc+b;
dem:=dem+1;
end;
if (c mod 2=1) then
begin
tbc:=tbc+c;
dem:=dem+1;
end;
if (d mod 2=1) then
begin
tbc:=tbc+d;
dem:=dem+1;
end;
if dem<>0 then
begin
tbc:=tbc/dem;
writeln('Ket qua: ',tbc:0:3);
end
else
writeln('Ket qua: -1');
readln;
end.