#include <stdio.h>

struct rt
{
    int l,r,max;
}t[900020];

int r[900020],SUM=0;

int maxa(int x,int y)
{
    return x>=y?x:y;
}
void make(int left,int right,int num)
{
    t[num].l=left;
    t[num].r=right;
    if(left==right)
        t[num].max=r[left];
    else
    {
        make(left,(left+right)/2,num+num);
        make((left+right)/2+1,right,num+num+1);
        t[num].max=maxa(t[num+num].max,t[num+num+1].max);
    }
}

void query(int left,int right,int num)
{
    if(left<=t[num].l&&right>=t[num].r)
        SUM=t[num].max>SUM?t[num].max:SUM;  //判断下，不然错的不要不要的
    else
    {
        if(left>(t[num].l+t[num].r)/2)
            query(left,right,num+num+1);
        if(right<=(t[num].r+t[num].l)/2)
            query(left,right,num+num);
        if(left<=(t[num].l+t[num].r)/2&&right>(t[num].l+t[num].r)/2)
        {
            query(left,right,num+num);
            query(left,right,num+num+1);
        }
    }
}

void change(int x,int y,int num)
{
    if(y>t[num].max)
        t[num].max=y;
    if(t[num].l==t[num].r)
    {
        //t[num].max=y;
        return ;
    }
    if(x>(t[num].r+t[num].l)/2)
        change(x,y,num+num+1);
    else
        change(x,y,num+num);

}
int main()
{
    int n,m,i,mi,ma,temp;
    char x;
    while(scanf("%d %d",&n,&m)!=EOF)
    {      
        for(i=1;i<=n;i++)
        {
            scanf("%d",&r[i]);
        }//getchar();
        make(1,n,1);
        for(i=0;i<m;i++)
        {
            getchar();scanf("%c %d %d",&x,&mi,&ma);  //getchar()很重要
            if(x==‘Q‘)
            {
                SUM=0;
                query(mi,ma,1);
                printf("%d\n",SUM);
            }
            if(x==‘U‘)
                change(mi,ma,1);

        }
    }
    return 0;
}