st-find the sum

#include<bits/stdc++.h>

using namespace std;

vector<long long> tree;

long long get_sum(int cur_node, int q_low, int q_high, int cur_low, int cur_high){


    if(q_low <= cur_low && q_high >= cur_high) return tree[cur_node];
    else if(q_low > cur_high || q_high < cur_low) return 0;
    else return get_sum(cur_node*2, q_low, q_high, cur_low, (cur_high+cur_low)/2) + get_sum(cur_node*2 + 1, q_low, q_high, (cur_high+cur_low)/2 + 1, cur_high);
}

int main()
{
    long long n, q;
    cin >> n >> q;
    long long i, x;
    vector < long long> v;
    for(i = 0; i < n; i++)
    {
        cin >> x;
        v.push_back(x);
    }
    while(__builtin_popcount(n) != 1)
    {
        n++;
        v.push_back(0LL);
    }
    tree.resize(2 * n);
    //for(i = 0; i < n; i++) cout << v[i] << " ";
    for(i = n; i < 2*n; i++) tree[i] = v[i-n];
    for(i = n - 1; i > 0; i--) tree[i] = tree[2*i] + tree[2*i + 1];
    while(q--)
    {
        long long l, r;
        cin >> l >> r;
        cout << get_sum(1, l, r, 1, n) << endl;
    }

}