segment of the segtree code. :D

int m[max_v], arr[max_v];
int n, q, s = 1; //n for size, q for query and s for something later
void make_tree(){
    while(s <= n) s *= 2; s *= 2;
    for(int i = s - 1; i < n + s - 1; i++){
        m[i] = arr[i - (s - 1)];
    }
    for(int i = s - 2; i >= 0; i--){
        m[i] = max(m[LC(i)], m[RC(i)]);
    }
}

void U(int p, int val, int k, int L, int R){
    if(L < p || p <= R || R <= L) return ;
    if(L + 1 == R){
        assert(L == p);
        m[k] = val;
        return ;
    }
    int mid = (L + R) / 2;
    U(p, val, LC(k), L, mid);
    U(p, val, RC(k), mid, R);
    m[k] = max(m[LC(k)], m[RC(k)]);
}

int Q(int qL, int qR, int k, int L, int R){
    if(qR <= L || R <= qL || R <= L) return 0;
    if(qL <= L && R <= qR) return m[k];
    int mid = (L + R) / 2;
    return max(Q(qL, qR, LC(k), L, mid), Q(qL, qR, RC(k), mid, R));
}