这玩意比较屌……

var
change:array[1..10,1..2]of ansistring;
s:array[0..2000]of string;
i,j,k,o,p,q,u,t,posi:longint;
a,b:ansistring;
begin
t:=-1;
while not(eof)do
begin
t:=t+1;
readln(s[t]);
end;
a:=copy(s[0],1,pos(' ',s[0])-1);
b:=copy(s[0],pos(' ',s[0])+1,length(s[0]));
for i:=1 to t do
begin
change[i,1]:=copy(s[i],1,pos(' ',s[i])-1);
change[i,2]:=copy(s[i],pos(' ',s[i])+1,length(s[i]));
end;
fillchar(s,sizeof(s),' ');
s[0]:=a;
i:=1;j:=0;k:=0;
while i<=10do
begin
q:=k+1;u:=k;
for p:=j to k do
begin
a:=s[p];
for o:=1 to t do
if pos(change[o,1],a)<>0 then
begin
u:=u+1;
s[u]:=a;
posi:=pos(change[o,1],s[u]);
delete(s[u],pos(change[o,1],s[u]),length(change[o,1]));
insert(change[o,2],s[u],posi);
if s[u]=b then begin write(i);halt;end;
end;
end;
j:=q;k:=u;
i:=i+1;
end;
if i>10 then write('NO ANSWER!');
end.

此代码能A，但wikioi上RE……