uses crt;
var x, y, z : integer; tb : real;
f1, f2: text;
begin
clrscr;
assign(f1, 'songuyen.dat'); reset(f1);
assign(f2, 'tbc.dat'); rewrite(f2);
readln(f1, x, y, z);
if (x mod 2 = 0) and (y mod 2 = 0) and (z mod 2 = 0)
then begin tb := (x + y + z)/ 3;
writeln(f2, tb : 2 : 1); end
else writeln(f2,'x, y, x khong chan');
close(f1); close(f2);
readln
end.