#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  cin >> n;
  long a[n + 1], b[n + 1];
  for (i = 0; i < n; i++) cin >> a[i];
  a[n] = 1;
  b[0] = 1;
  for (i = 1; i <= n; i++) {
    b[i] = (2 * b[i - 1] - b[a[i - 1] - 1] + 2) % 1000000007;
    if (b[i] < 0) b[i] += 1000000007;
  }
  cout << (b[n] - 1);
  return 0;
}
