HDU-I Hate It

#include<cstdio>
#include<cstring>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;

#define INF 0x3f3f3f3f
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1

const int MX = 222222;
int sum[MX<<2];
int n, q;

void push_up(int rt) {
    sum[rt] = max(sum[rt<<1], sum[rt<<1|1]);
}
void Build(int l, int r, int rt) {
    if (l == r) {
        scanf("%d", &sum[rt]);
        return ;
    }
    int m = (l + r)>>1;
    Build(lson);
    Build(rson);
    push_up(rt);
}
void update(int pos, int add, int l, int r, int rt) {
    if (l == r) {
        sum[rt] = add;
        return ;
    }
    int m = (l + r)>>1;
    if (pos <= m) update(pos, add, lson);
    else update(pos, add, rson);
    push_up(rt);
}
int Query(int L, int R, int l, int r, int rt) {
    if (L <= l && r <= R) {
        return sum[rt];
    }
    int m = (l + r)>>1;
    int Max = -INF;
    if (L <= m) Max = max(Max, Query(L, R, lson));
    if (R > m) Max = max(Max, Query(L, R, rson));
    return Max;
}
int main() {
    //freopen("input.txt", "r", stdin);
    while (scanf("%d %d", &n, &q) != EOF) {
        memset(sum, 0, sizeof(sum));

        Build(1, n, 1);
        while (q--) {
            char ch[5];
            int i, j;
            scanf("%s %d %d", ch, &i, &j);
            if (ch[0] == ‘Q‘) {
                printf("%d\n", Query(i, j, 1, n, 1));
            } else {
                update(i, j, 1, n, 1);
            }
        }
    }
    return 0;
}