1 var head,vet,next,s,b,stack,low,dfn,flag:array[1..200000]of longint; 2     n,i,ans,tot,id,top,time,x:longint; 3  4 procedure add(a,b:longint); 5 begin 6  inc(tot); 7  next[tot]:=head[a]; 8  vet[tot]:=b; 9  head[a]:=tot;10 end;11 12 function min(x,y:longint):longint;13 begin14  if x<y then exit(x);15  exit(y);16 end;17 18 procedure dfs(u:longint);19 var e,v:longint;20 begin21  flag[u]:=1;22  inc(top); stack[top]:=u;23  inc(time); dfn[u]:=time; low[u]:=time;24  e:=head[u];25  while e<>0 do26  begin27   v:=vet[e];28   if flag[v]=0 then29   begin30    dfs(v);31    low[u]:=min(low[u],low[v]);32   end33    else if s[v]=0 then low[u]:=min(low[u],low[v]);34   e:=next[e];35  end;36 37  if low[u]=dfn[u] then38  begin39   inc(id); s[u]:=id; inc(b[id]);40   while (top>0)and(stack[top]<>u) do41   begin42    s[stack[top]]:=id;43    inc(b[id]);44    stack[top]:=0;45    dec(top);46   end;47   stack[top]:=0;48   dec(top);49  end;50 end;51 52 begin53  //assign(input,‘1.in‘); reset(input);54  //assign(output,‘1.out‘); rewrite(output);55  readln(n);56  for i:=1 to n do57  begin58   read(x);59   add(i,x);60  end;61  for i:=1 to n do62   if flag[i]=0 then dfs(i);63  ans:=n;64  for i:=1 to id do65   if (b[i]>1)and(b[i]<ans) then ans:=b[i];66  if n=1 then writeln(0)67   else writeln(ans);68  //close(input);69  //close(output);70 end.