int lg[N], f[N][19];

void init(){
    lg[1] = 0, lg[2] = 1;
    for(int i = 3;i < N;i ++ )
        lg[i] = lg[i >> 1] + 1;
}

void ST_prework(){
    for(int i = 1;i <= n;i ++ ) f[i][0] = a[i];

    for(int j = 1;j <= 18;j ++ )
        for(int i = 1;i + (1 << j) - 1 <= n;i ++ )
            f[i][j] = max(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
}

int ST_query(int l,int r){
    int k = lg[r - l + 1];
    return max(f[l][k], f[r - (1 << k) + 1][k]);
}