Фенвик

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <math.h>
#include <climits>

//#pragma GCC optimize("O3, unroll-loops");

#include <list>
#include <map>
#include <set>
#include <queue>
#include <unordered_map>
#include <unordered_set>

//#include <chrono>
//#include <fstream>
//#include <bits/stdc++.h>

#define mp make_pair
#define pb push_back
#define eb emplace_back
#define x first
#define y second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b) - 1; i >= (a); i--)

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> veci;
typedef vector<bool> vecb;
typedef vector<vector<int>> vvi;
typedef vector<vector<bool>> vvb;

const int INF_I = 1e9;
const ll INF_LL = 1e18;

int n;
vector<ll> t;
vector<ll> a;

ll sum(int r) {
    ll res = 0;
    for (; r >= 0; r = ((r + 1) & r) - 1)
        res += (ll)t[r];
    return res;
}

ll sum(int l, int r) {
    return sum(r) - sum(l - 1);
}

void update(int i, ll val) {
    ll d = val - a[i];
    a[i] = val;
    for (; i < n; i = i | (i + 1)) {
        t[i] += d;
    }
}

int main() {
    /*ifstream cin("in.txt");
    ofstream cout("out.txt");
    auto start_time = chrono::high_resolution_clock::now();*/

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);


    cin >> n;
    t.assign(n, 0);
    a.assign(n, 0);
    for (int i = 0; i < n; i++) {
        ll val;
        cin >> val;
        update(i, val);
    }
    int m;
    cin >> m;
    for (int i = 0; i < m; i++) {
        char ch;
        cin >> ch;
        if (ch == 'u') {
            ll index, val;
            cin >> index >> val;
            update(--index, val);
        }
        else {
            int l, r;
            cin >> l >> r;
            cout << sum(--l, --r) << " ";
        }
    }

    /*auto end_time = chrono::high_resolution_clock::now();
    chrono::duration<double> duration = end_time - start_time;
    cout << duration.count() << "\n";
    cin.close();
    cout.close();*/
    return 0;
}