{
ZADATAK: proizvod
JEZIK: PASCAL
}
PROGRAM PROIZVOD;
VAR
  N,I,CI,MI : LONGINT;
  PR : QWORD;
  CENAI,MARZAI : LONGINT;
  M : INTEGER;
  C : ARRAY[1..100001] OF CHAR;
  CENA : ARRAY[1..100001] OF CHAR;
  MARZA : ARRAY[1..100001] OF CHAR;
  PRC: ARRAY[1..9] OF CHAR;
  PRS : STRING;

  PROCEDURE LOAD;
  VAR
    FIN : TEXT;
  BEGIN
    ASSIGN(FIN,'proizvod.in');
    RESET(FIN);
      READLN(FIN, N, M);
      FOR I:=1 TO N DO READ(FIN,C[I]);
    CLOSE(FIN);
  END;

  PROCEDURE SORT(LO,HI:LONGINT);
  VAR
    LEFT,RIGHT:INTEGER;
    PIVOT,SWAP:CHAR;
  BEGIN
    LEFT:=LO;
    RIGHT:=HI;
    IF (LEFT<>0) AND (RIGHT<>0) THEN PIVOT:=C[(LEFT+RIGHT) DIV 2];
    WHILE LEFT<=RIGHT DO BEGIN
      WHILE C[LEFT]>PIVOT DO INC(LEFT);
      WHILE C[RIGHT]<PIVOT DO DEC(RIGHT);
      IF LEFT<=RIGHT THEN BEGIN
        SWAP:=C[LEFT];
        C[LEFT]:=C[RIGHT];
        C[RIGHT]:=SWAP;
        INC(LEFT);
        DEC(RIGHT);
      END;
    END;
    IF LEFT>LO THEN SORT(LO,RIGHT);
    IF RIGHT<HI THEN SORT(LEFT,HI);
  END;

  PROCEDURE MAKEC;
  BEGIN
    CI:=1;
    MI:=1;
    I:=1;
    WHILE I<=N DO BEGIN
      IF ((I DIV 4) MOD 2=0) THEN BEGIN
        IF C[I]<>#0 THEN BEGIN
          CENA[CI]:=C[I];
          INC(CI);
          INC(I);
        END;
        IF C[I]<>#0 THEN BEGIN
          MARZA[MI]:=C[I];
          INC(MI);
          INC(I);
        END;
        IF C[I]<>#0 THEN BEGIN
          MARZA[MI]:=C[I];
          INC(I);
          INC(MI);
        END;
        IF C[I]<>#0 THEN BEGIN
          CENA[CI]:=C[I];
          INC(I);
          INC(CI);
        END;
      END
      ELSE IF ((I DIV 4) MOD 2=1) THEN BEGIN
       IF C[I]<>#0 THEN BEGIN
          MARZA[MI]:=C[I];
          INC(MI);
          INC(I);
        END;
        IF C[I]<>#0 THEN BEGIN
          CENA[CI]:=C[I];
          INC(CI);
          INC(I);
        END;
        IF C[I]<>#0 THEN BEGIN
          CENA[CI]:=C[I];
          INC(I);
          INC(CI);
        END;
        IF C[I]<>#0 THEN BEGIN
          MARZA[MI]:=C[I];
          INC(I);
          INC(MI);
        END;
      END;
    END;
  END;

  FUNCTION POWER( A : INTEGER) : QWORD;
  VAR
    PI : INTEGER;
    PREZ : QWORD;
  BEGIN
    PREZ:=1;
    IF A=0 THEN PREZ:=1;
    FOR PI:= 1 TO A DO BEGIN
      PREZ:=PREZ*10;
    END;
    POWER:=PREZ;
  END;

  PROCEDURE MAKEI;
  VAR
    VALI : INTEGER;
    PC : CHAR;
  BEGIN
    CENAI:=0;
    MARZAI:=0;
    CI:=CI-1;
    MI:=MI-1;
    I:=0;
    WHILE (I<=7) AND (CI-I>0) DO BEGIN
      VAL(CENA[CI-I],VALI);
      CENAI:=CENAI+VALI*POWER(I);
      INC(I);
    END;
    I:=0;
    WHILE (I<=7) AND (MI-I>0) DO BEGIN
      VAL(MARZA[MI-I],VALI);
      MARZAI:=MARZAI+VALI*POWER(I);
      INC(I);
    END;
    PR:=CENAI*MARZAI;
    FOR I:=1 TO 9 DO PRC[I]:=#0;
    STR(PR,PRS);
    FOR I:=1 TO M DO BEGIN
      PRC[M-I+1]:=PRS[LENGTH(PRS)-I+1];
    END;
    FOR I:=1 TO M-LENGTH(PRS) DO PRC[I]:='0';
  END;

  PROCEDURE UNLOAD;
  VAR
    FOUT : TEXT;
  BEGIN
    ASSIGN(FOUT,'proizvod.out');
    REWRITE(FOUT);
    FOR I:=1 TO M DO BEGIN
      WRITE(FOUT,PRC[I]);
    END;
    CLOSE(FOUT);
  END;

BEGIN
  LOAD;
  SORT(1,N);
  MAKEC;
  MAKEI;
  UNLOAD;
END.

