1 #include<stdio.h>
 2 #include<string.h>
 3 #define lson root<<1,l,mid
 4 #define rson root<<1|1,mid+1,r
 5 const int MAXN=200010<<2;
 6 #define X int root,int l,int r
 7 #define Y 1,1,N
 8 #define MAX(x,y)(x>y?x:y)
 9 #define NOW tree[root]=MAX(tree[root<<1],tree[root<<1|1])
10 int tree[MAXN];
11 int A,B,anser;
12 void build(X){
13     if(l==r)scanf("%d",&tree[root]);
14     else {
15         int mid=(l+r)>>1;
16         build(lson);
17         build(rson);
18         NOW;
19     }
20 }
21 void update(X){
22     if(l==A&&r==A)tree[root]=B;
23     else{
24         int mid=(l+r)>>1;
25         if(A<=mid)update(lson);
26         else update(rson);
27         NOW;
28     }
29 }
30 void print(X){
31     if(A<=l&&B>=r)anser=MAX(anser,tree[root]);//这个是从线段树的顶往下搜的 
32     else{
33         int mid=(l+r)>>1;
34         if(A<=mid)print(lson);//记住mid 
35         if(B>mid)print(rson);
36         NOW;
37     }
38 }
39 int main(){
40     int N,M;
41     char s[2];
42     while(~scanf("%d%d",&N,&M)){
43         build(Y);
44         while(M--){
45             scanf("%s",s);
46         if(!strcmp(s,"U")){
47             scanf("%d%d",&A,&B);
48             update(Y);
49         }
50         else{
51             anser=0;
52             scanf("%d%d",&A,&B);
53             print(Y);
54             printf("%d\n",anser);
55         }
56         }
57     }
58     return 0;
59 }