1 const dd:array[1..4,1..2] of longint=((1,0),(-1,0),(0,-1),(0,1));
2 var
3 i,j,k,l,m,n,x0,y0,x1,y1,x,y,f,r:longint;
4 a,b:array[0..1000,0..1000] of longint;
5 tr:array[2..27,1..4] of longint;
6 d:array[0..1000000,1..2] of longint;
7 ch:char;
8 procedure trans(z:longint;var x,y:longint);
9 begin
10 if (z<2) or (z>27) then exit;
11 if (tr[z,1]=x) and (tr[z,2]=y) then
12 begin
13 x:=tr[z,3];y:=tr[z,4];
14 end
15 else if (tr[z,3]=x) and (tr[z,4]=y) then
16 begin
17 x:=tr[z,1];y:=tr[z,2];
18 end;
19 end;
20 begin
21 readln(n,m);
22 fillchar(a,sizeof(a),-1);
23 fillchar(tr,sizeof(tr),0);
24 for i:=1 to n do
25 begin
26 for j:=1 to m do
27 begin
28 read(ch);
29 case upcase(ch) of
30 ‘#‘:a[i,j]:=1;
31 ‘.‘:a[i,j]:=0;
32 ‘=‘:begin
33 x1:=i;y1:=j;
34 a[i,j]:=0;
35 end;
36 ‘@‘:begin
37 x0:=i;y0:=j;
38 a[i,j]:=1;
39 end;
40 ‘A‘..‘Z‘:begin
41 a[i,j]:=ord(ch)-63;
42 if tr[a[i,j],1]=0 then
43 begin
44 tr[a[i,j],1]:=i;
45 tr[a[i,j],2]:=j;
46 end
47 else
48 begin
49 tr[a[i,j],3]:=i;
50 tr[a[i,j],4]:=j;
51 end;
52 end;
53 end;
54 end;
55 readln;
56 end;
57 f:=1;r:=2;d[1,1]:=x0;d[1,2]:=y0;b[x0,y0]:=1;
58 while f<r do
59 begin
60 for i:=1 to 4 do
61 begin
62 x:=d[f,1]+dd[i,1];
63 y:=d[f,2]+dd[i,2];
64 if (x<1) or (x>n) or (y<1) or (y>m) then continue;
65 if abs(a[x,y])=1 then continue;
66 trans(a[x,y],x,y);
67 if b[x,y]=0 then
68 begin
69 b[x,y]:=b[d[f,1],d[f,2]]+1;
70 d[r,1]:=x;d[r,2]:=y;
71 if (x=x1) and (y=y1) then
72 begin
73 writeln(b[x,y]-1);
74 halt;
75 end;
76 inc(r);
77 end;
78 end;
79 inc(f);
80 end;
81 end.