1 var
2 i,j,k,l,n,m,dts,y,a,b:longint;
3 fa,sm,v,rev,dt:array[0..50001]of longint;
4 ch:array[0..50001,0..1]of longint;
5 ch1,ch2:char;
6 procedure update(x:longint);
7 begin
8 if x=0 then exit; sm[x]:=v[x];
9 if ch[x,0]<>0 then sm[x]:=sm[x]+sm[ch[x,0]];
10 if ch[x,1]<>0 then sm[x]:=sm[x]+sm[ch[x,1]];
11 end;
12 function isroot(x:longint):boolean;
13 begin
14 if(x=0)or(fa[x]=0)then exit(true);
15 exit((x<>ch[fa[x],0])and(x<>ch[fa[x],1]));
16 end;
17 procedure pushdown(x:longint);
18 var tt:longint;
19 begin
20 if rev[x]=1 then
21 begin
22 tt:=ch[x,1]; ch[x,1]:=ch[x,0]; ch[x,0]:=tt; rev[x]:=0;
23 if ch[x,0]<>0 then rev[ch[x,0]]:=rev[ch[x,0]]xor 1;
24 if ch[x,1]<>0 then rev[ch[x,1]]:=rev[ch[x,1]]xor 1;
25 end;
26 end;
27 procedure rotate(x:longint);
28 var a1,a2,a3,b1,b2,b3:longint;
29 begin
30 if(x=0)or(isroot(x))then exit;
31 a1:=fa[x]; a2:=fa[fa[x]];
32 if x=ch[a1,1] then b1:=1 else b1:=0;
33 if a1=ch[a2,1] then b2:=1 else b2:=0;
34 if isroot(a1)then b3:=1 else b3:=0; a3:=ch[x,1-b1];
35 if b3=0 then ch[a2,b2]:=x; fa[x]:=a2; ch[a1,b1]:=a3;
36 if a3>0 then fa[a3]:=a1; ch[x,1-b1]:=a1; fa[a1]:=x;
37 update(a1); update(x); if b3=0 then update(a2);
38 end;
39 procedure splay(x:longint);
40 begin
41 if x=0 then exit; dts:=0; y:=x;
42 while not isroot(y) do begin inc(dts); dt[dts]:=y; y:=fa[y]; end;
43 inc(dts); dt[dts]:=y; while dts>0 do begin pushdown(dt[dts]); dec(dts); end;
44 while not isroot(x) do
45 begin
46 if not isroot(fa[x]) then
47 begin
48 if(x=ch[fa[x],1])xor(fa[x]=ch[fa[fa[x]],1])
49 then rotate(x) else rotate(fa[x]);
50 end;
51 rotate(x);
52 end;
53 end;
54 function access(x:longint):longint;
55 var t:longint;
56 begin
57 if x=0 then exit(0); t:=0;
58 while x>0 do
59 begin
60 splay(x); ch[x,1]:=t; update(x);
61 if t>0 then fa[t]:=x; t:=x; x:=fa[x];
62 end;
63 exit(t);
64 end;
65 procedure cut(x,y:longint);
66 begin
67 if(x=0)and(y=0)then exit;
68 access(x); splay(x); rev[x]:=rev[x]xor 1;
69 access(y); splay(x); fa[y]:=0; ch[x,1]:=0; update(x);
70 end;
71 procedure link(x,y:longint);
72 begin
73 if(x=0)and(y=0)then exit;
74 access(x); splay(x); rev[x]:=rev[x]xor 1; fa[x]:=y;
75 end;
76 function qsum(x,y:longint):longint;
77 var a:longint;
78 begin
79 if(x=0)or(y=0)then exit(0); if x=y then exit(v[x]);
80 access(x); a:=access(y); splay(x);
81 if x=a then exit(v[a]+sm[ch[a,1]])else exit(sm[x]+v[a]+sm[ch[a,1]]);
82 end;
83 procedure change(x,y:longint);
84 begin
85 splay(x); v[x]:=y; update(x);
86 end;
87 function find(x:longint):longint;
88 begin
89 access(x); splay(x); while ch[x,0]>0 do x:=ch[x,0]; exit(x);
90 end;
91 begin
92 readln(n); for i:=1 to n do read(v[i]); sm[i]:=v[i]; readln(m);
93 for i:=1 to m do
94 begin
95 read(ch1); read(ch2); while ch2<>‘ ‘ do read(ch2); readln(a,b);
96 if ch1=‘b‘ then
97 begin
98 if find(a)=find(b) then writeln(‘no‘)else
99 begin writeln(‘yes‘); link(a,b); end;
100 end else if ch1=‘p‘ then change(a,b) else
101 if find(a)<>find(b) then writeln(‘impossible‘)else writeln(qsum(a,b));
102 end;
103 end.
