3a b c

c A B b A C a A D b C D c B D

program p1_7(input,output);var ga,gb,gc,gd,fd:array [0..15] of char; topa,topb,topc,topf:byte; resl:array [1..2000] of record                          code:char;                          source:char;                          target:char                        end; order:array [‘0‘..‘z‘] of byte; i,n,kz,ks:byte; j:char;procedure print;var i:byte;begin i:=1; repeat   writeln(resl[i].code:5,resl[i].source:5,resl[i].target:5);   inc(i) until resl[i].code=‘0‘;end;procedure move1(var topa,topb,topc,ks:byte);var t:byte;begin  repeat   if  (topa=0)and(topb=0)and(topc=0) then     begin  print;halt(1);kz:=1 end;   t:=0;   if  ga[topa]=fd[topf] then    begin{a-d}       t:=t+1;       ks:=ks+1;       resl[ks].code:=ga[topa];       resl[ks].source:=‘A‘;       resl[ks].target:=‘D‘;       topf:=topf+1;topa:=topa-1;    end;  if  gb[topb]=fd[topf] then    begin{b-d}      t:=t+1;      ks:=ks+1;      resl[ks].code:=gb[topb];      resl[ks].source:=‘B‘;      resl[ks].target:=‘D‘;      topf:=topf+1;topb:=topb-1;    end;  if  gc[topc]=fd[topf] then    begin {c-d}      t:=t+1;      ks:=ks+1;      resl[ks].code:=gc[topc];      resl[ks].source:=‘C‘;      resl[ks].target:=‘D‘;      topf:=topf+1;topc:=topc-1;    end;  until t=0;end;procedure move2(var topa,topb,topc,ks: byte);var   tp,ks1:byte;begin  move1(topa,topb,topc,ks);  ks1:=ks+1;  for  tp:=1  to  3  do      case tp  of      1: {a--b}       if  topa>0 then        begin         resl[ks1].code:=ga[topa];         resl[ks1].source:=‘A‘;         resl[ks1].target:=‘B‘;         topb:=topb+1;gb[topb]:=ga[topa];topa:=topa-1;         move2(topa,topb,topc,ks1);         topa:=topa+1;dec(topb);        end;       2: {a--c}       if (order[ga[topa]]<order[gc[topc]])and(topa>0) then        begin         resl[ks1].code:=ga[topa];         resl[ks1].source:=‘A‘;         resl[ks1].target:=‘C‘;         topc:=topc+1;gc[topc]:=ga[topa];topa:=topa-1;         move2(topa,topb,topc,ks1);         topa:=topa+1;dec(topc);        end;       3: {b--c}        if (order[gb[topb]]<order[gc[topc]])and(topb>0)then         begin           resl[ks1].code:=gb[topb];           resl[ks1].source:=‘B‘;           resl[ks1].target:=‘C‘;           topc:=topc+1;gc[topc]:=gb[topb];dec(topb);           move2(topa,topb,topc,ks1);           topb:=topb+1;dec(topc)           end;     end{case and  for};end;begin{main}  assign(input,‘word.in‘);  reset(input);  assign(output,‘word.out‘);  rewrite(output);  readln(n);  for  i:=1  to  n  do    read(fd[i]);  i:=1;repeat for  j:=‘a‘ to chr(ord(‘a‘)+n-1) do if j=fd[i] then order[j]:=i;i:=i+1until i>n;order[‘0‘]:=0;order[‘1‘]:=100;for i:=1 to 200 do resl[i].code:=‘0‘;for i:=1 to n do ga[i]:=chr(ord(‘a‘)+i-1);topa:=n;topb:=0;topc:=0;topf:=1;kz:=0;ks:=0;ga[0]:=‘0‘;gb[0]:=‘0‘;gc[0]:=‘1‘;move2(topa,topb,topc,ks);if kz=0 then writeln(‘no solution!‘);end.