LL exgcd(LL x,LL y){

      printf("%lld %lld\n",x,y);

      if (y==){

        xx=;yy=;return(x);

    }

    LL ret=exgcd(y,x%y);

    LL t=xx;xx=yy;yy=t-(x/y)*yy;

    return(ret);

  }

 procedure exgcd(a,b:int64);

  var

   t:longint;

    begin

      if  b= then

        begin

          x:=;y:=;

          exit;

        end else

       exgcd(b,a mod b);

       t:=x;x:=y;y:=t-(a div b)*y;

    end;

  function cfny(a:int64):int64;

  var

    b:longint;

     begin

       b:=zs;

       exgcd(a,b);

       cfny:= ((x mod zs)+zs) mod zs;

     end;