#include <bits/stdc++.h>
using namespace std;
int N, P[1005], D[1005];
int main() {
  scanf("%d", &N);
  for (int i = 1; i <= N; i++) {
    scanf("%d", &P[i]);
  }
  D[1] = 1;
  for (int i = 2; i <= N; i++) {
    int p = P[i];
    D[i] = 1;
    for (int j = p; j < i; j++) {
      D[i] += D[j] + 1;
      D[i] %= 1000000007;
    }
  }
  int res = 0;
  for (int i = 1; i <= N; i++) {
    res += D[i] + 1;
    res %= 1000000007;
  }
  printf("%d\n", res);
  return 0;
}
