#include <bits/stdc++.h>
using namespace std;
int k[1005], n, i, j;
long long kx[1005];
int main() {
  cin >> n;
  for (i = 1; i <= n; i++) cin >> k[i];
  kx[1] = 2;
  for (i = 2; i <= n; i++) {
    if (k[i] == i)
      kx[i] = 2;
    else {
      for (j = k[i]; j < i; j++) kx[i] = (kx[i] + kx[j]) % 1000000007;
      kx[i] = (kx[i] + 2) % 1000000007;
    }
  }
  long long ans = 0;
  for (i = 1; i <= n; i++) ans = (ans + kx[i]) % 1000000007;
  cout << ans;
  return 0;
}
