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  1. #include <iostream>
  2. #include <cstdio>
  3. using namespace std;
  4.  
  5. int main() {
  6. 	int n, p[1005], a[1005], r;
  7. 	const int md=1e9+7;
  8. 	r=0;
  9. 	scanf("%d", &n);
  10. 	for(int i=1; i<=n; i++) scanf("%d", &p[i]);
  11. 	for(int i=1; i<=n; i++) {
  12. 		a[i]=2;
  13. 		for(int j=p[i]; j<i; j++) a[i]+=a[j], a[i]%=md;
  14. 		r+=a[i], r%=md;
  15. 	}
  16. 	printf("%d", r);
  17. 	return 0;	
  18. }
Success #stdin #stdout 0s 3344KB
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https://ideone.com/UO6jUA
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
public

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