function c=gongyuesu(a,b)
if a<b
    t=a;
    a=b;
    b=t;
end
c=b;
r=rem(a,b);
q=fix(a/b);
while r~=0
    a=b;
    b=r;
    c=r;
    r=rem(a,b);
    q=fix(a/b);
end
c=abs(c);