{ This program is correct wrt the CF grammar. }

program example;

var x, y, x: integer; { x is redeclared within one var statement }
function gcd(a,b: integer): integer;
var c: integer; 
var d,e,f: integer;
var c: integer; { c is redeclared }
begin
    if b = 0 then gcd := a
    else gcd := gcd(b, a mod b)
end;

begin
    x := readinteger; y := readinteger;
    writeinteger(gcd(x, y))
end.