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#include <bits/stdc++.h>
using namespace std;

const int maxn = 1e3;

int cur;
int n;
vector<int> num(maxn);
int tree[maxn << 1];

void push_up(int rt) {
    tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
}

void build(int l, int r, int rt) {
    if (l == r) {
        tree[rt] = num[cur++];
        return;
    }
    int m = (r + l) / 2;
    build(l, m, rt << 1);
    build(m + 1, r, rt << 1 | 1);
    push_up(rt);
}

void update(int idx, int num, int l, int r, int rt) {
    if (l == r) {
        tree[rt] = num;
        return;
    }
    int m = (r + l) / 2;
    if (idx <= m) {
        update(idx, num, l, m, rt << 1);
    }
    else {
        update(idx, num, m + 1, r, rt << 1 | 1);
    }
    push_up(rt);
}

int query(int L, int R, int l, int r, int rt) {
    if (L <= l && r <= R) {
        return tree[rt];
    }
    int m = (r + l) / 2;
    int ans = 0;
    if (L <= m) {
        ans += query(L, R, l, m, rt << 1);
    }
    if (R > m) {
        ans += query(L, R, m + 1, r, rt << 1 | 1);
    }
    return ans;
}


int main() {
    num = vector<int>({1, 2, 1, 2, 3, 4});
    int n = num.size();

    build(1, n, 1);
    for (int i = 1; i <= n; i++) {
        cout << tree[i];
    }

    cout << query(1, 4, 1, n, 1) << '\n';
    update(1, 3, 1, n, 1);
    cout << query(1, 4, 1, n, 1) << '\n';
    return 0;
}