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  1. #include<stdio.h>
  2.  
  3.  
  4.  
  5. long long int a[1000005];
  6. int n;
  7.  
  8. int dp(int n) {
  9. 	if (n == 1)return 0;
  10. 	if (n == 2)return 1;
  11. 	if (a[n] != 0) return a[n];
  12. 	return a[n] = (n-1)*(dp(n-1)+dp(n-2)) % 1000000000;
  13. }
  14.  
  15. int main() {
  16. 	scanf("%d", &n);
  17. 	printf("%d", dp(n));
  18.  
  19.  
  20.  
  21.  
  22.  
  23. }
Success #stdin #stdout 0s 22288KB
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-836908074
https://ideone.com/uGuYa6
language:
C (gcc 8.3)
created:
5 years ago
visibility:
public

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