Calcular suma del rango a-b

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int N, Q, a, b;
    cin >> N;

    vector <int> v(N);

    for(int i=0; i<N; i++)
        cin >> v[i];

    vector <int> sumas(N+1);
    sumas[0] = 0;
    for(int i=1; i<N+1; i++)
        sumas[i] = sumas[i-1] + v[i-1];

    cin >> Q;

    for(int i=0; i<Q; i++)
    {
        cin >> a >> b;
        cout << sumas[b+1] - sumas[a] << endl;
    }

    return 0;
}