Revise paste 3cba4975914af

#include <iostream>
#include <set>
using namespace std;
const int maxn = 200005;
typedef long long ll;
const int INF = 2e9;
int n, a[maxn];

ll segment_tree[3 * maxn];

ll merge_nodes(ll A, ll B) {
    return A + B;
}

void build_tree(int L = 0, int R = n - 1, int node = 1) {
    if(L == R) {
        segment_tree[node] = a[L];
    }
    else {
        int middle = (L + R) / 2;
        build_tree(L, middle, 2 * node);
        build_tree(middle + 1, R, 2 * node + 1);
        segment_tree[node] = merge_nodes(segment_tree[2 * node], segment_tree[2 * node + 1]);
    }
}

ll query(int i, int j, int L = 0, int R = n - 1, int node = 1) {
    if(R < i or j < L) {
        return 0;
    }
    if(i <= L and R <= j) {
        return segment_tree[node];
    }
    
    int middle = (L + R) / 2;
    ll left_side = query(i, j, L, middle, 2 * node);
    ll right_side = query(i, j, middle + 1, R, 2 * node + 1);
    
    return merge_nodes(left_side, right_side);
}
int main() {
    ios_base::sync_with_stdio(false);
    int q;
    
    cin >> n >> q;
    
    for(int i = 0; i < n; i++) {
        cin >> a[i];
    }
    build_tree();
    
    for(int i = 0; i < q; i++) {
        int a, b;
        cin >> a >> b;
        
        a--; b--;
        
        cout << query(a, b) << endl;
    }

return 0;
}