线段树（单点更新） 之 hdu 1754

//  [7/25/2014 Sjm]
/*
线段树单点更新水题。。。
*/

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <algorithm>
using namespace std;
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define GetMid l + ((r-l)>>1)

const int MAX_N = 200005;
int MAX[MAX_N << 2];

void PushUp(int rt) { MAX[rt] = max(MAX[rt << 1], MAX[rt << 1 | 1]); }

void Build(int l, int r, int rt) {
	if (l == r) { scanf("%d", &MAX[rt]); return; }
	int m = GetMid;
	Build(lson);
	Build(rson);
	PushUp(rt);
}

void Update(int p, int grade, int l, int r, int rt) {
	if (l == r) { MAX[rt] = grade; return; }
	int m = GetMid;
	if (p <= m) { Update(p, grade, lson); }
	else { Update(p, grade, rson); }
	PushUp(rt);
}
int Query(int L, int R, int l, int r, int rt) {
	if (L <= l && r <= R) { return MAX[rt]; }
	int m = GetMid;
	int ans = 0;
	if (L <= m) { ans = max(ans, Query(L, R, lson)); }
	if (R > m) { ans = max(ans, Query(L, R, rson)); }
	return ans;
}

int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int N, M, a, b;
	char ch[2];
	while (~scanf("%d %d", &N, &M)) {
		Build(1, N, 1);
		while (M--) {
			scanf("%s %d %d", ch, &a, &b);
			if ('Q' == ch[0]) { printf("%d\n", Query(a, b, 1, N, 1)); }
			else  { Update(a, b, 1, N, 1); }
		}
	}
	return 0;
}