#include <bits/stdc++.h>
using namespace std;
map<long long int, long long int> mp, mk;
set<long long int> s1, s2;
vector<long long int> v, w;
long long int a[2000006], b[2000006];
string s = "", p = "", q = "";
char ch;
long long int m, n, c, d, i, j, k, l, r, x, t, y, u, e, f, g, h;
int main() {
  cin >> n;
  for (i = 1; i < n; i++) cin >> a[i];
  cin >> c >> d;
  for (i = c; i < d; i++) u += a[i];
  cout << u;
}
