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