#include <bits/stdc++.h>
using namespace std;
long long power(long long a, long long p, long long mod) {
  long long ret = 1;
  while (p) {
    if (p & 1) ret = (ret * a) % mod;
    a = (a * a) % mod;
    p /= 2;
  }
  return ret;
}
long long DP[1000];
int A[1000];
int main() {
  int n;
  cin >> n;
  for (__typeof((__typeof(n))0) i((__typeof(n))0); i < n; i++) {
    cin >> A[i];
    A[i]--;
  }
  for (int i = 0; i < n; i++) {
    DP[i] = 2;
    for (int j = A[i]; j < i; j++) DP[i] = (DP[i] + DP[j]) % 1000000007;
  }
  long long ans = 0;
  for (int i = 0; i < n; i++) ans = (ans + DP[i]) % 1000000007;
  cout << ans << endl;
  return 0;
}
