#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<string>
#include<algorithm>
#include<cstdlib>
#include<set>
#include<queue>
#include<stack>
#include<vector>
#include<map>

#define N 200010
#define Mod 10000007
#define lson l,mid,idx<<1
#define rson mid+1,r,idx<<1|1
#define lc idx<<1
#define rc idx<<1|1
const double EPS = 1e-11;
const double PI = acos ( -1.0 );
const double E = 2.718281828;
typedef long long ll;

const int INF = 1000010;

using namespace std;

int tree[N<<2];
int m,n;

void push_up(int idx)
{
    tree[idx]=max(tree[lc],tree[rc]);
}

void build(int l,int r,int idx)
{
    if(l==r)
    {
        scanf("%d",&tree[idx]);
        return;
    }
    int mid=(l+r)>>1;
    build(lson);
    build(rson);
    push_up(idx);
}

void update(int l,int r,int idx,int x,int k)
{
    if(l==r)
    {
        tree[idx]=k;
        return ;
    }
    int mid=(l+r)>>1;
    if(x<=mid)
        update(lson,x,k);
    if(x>mid)
        update(rson,x,k);
    push_up(idx);
}

int query(int l,int r,int idx,int x,int y)
{
    if(x<=l&&y>=r)
        return tree[idx];
    int mid=(l+r)>>1;
    int s=-1;
    if(x<=mid)
        s=max(s,query(lson,x,y));
    if(y>mid)
        s=max(s,query(rson,x,y));
    return s;
}

int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        build(1,n,1);
        char s[2];
        int x,y;
        while(m--)
        {
            scanf("%s%d%d",s,&x,&y);
            if(s[0]=='U')
                update(1,n,1,x,y);
            else
                printf("%d\n",query(1,n,1,x,y));
        }
    }
    return 0;
}