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  1. #include <cstdio>
  2. int n, m, k, v;
  3. int pr[200005], pn, pl[200005], bn, cnt[30005];
  4. long long d[30005 * 3]; //binary indexed tree
  5. long long X, Y;
  6. long long mul(int a, int b) {
  7. 	X = 1; Y = a;
  8. 	while (b) {
  9. 		if (b & 1) X = (X*Y) % m;
  10. 		Y *= Y; b /= 2;
  11. 	}
  12. 	return X;
  13. }
  14. void upd(int x, int y) {
  15. 	cnt[x] += y;
  16. 	d[bn + x] = mul(pr[x], cnt[x]);
  17. 	x += bn;
  18. 	x /= 2;
  19. 	while (x) {
  20. 		d[x] = (d[2 * x] * d[2 * x + 1]) % m;
  21. 		x /= 2;
  22. 	}
  23. }
  24. int main() {
  25. 	for (int i = 2; i <= 200000; i += 2) pl[i] = 1;
  26. 	pr[++pn] = 2;
  27. 	for (int i = 3; i <= 200000; i += 2) {
  28. 		if (!pl[i]) {
  29. 			pr[++pn] = i;
  30. 			for (int j = i; j <= 200000; j += i) pl[j] = pn;
  31. 		}
  32. 	}
  33. 	bn = 1;
  34. 	while (bn < pn) bn *= 2;
  35. 	bn--;
  36. 	for (int i = 1; i < 2 * (bn + 1); i++) d[i] = 1;
  37. 	scanf("%d%d", &n, &m);
  38. 	n -= 2;
  39. 	long long res = 1, s;
  40. 	for (int i = 2; i <= n; i++) {
  41. 		upd(1, 1);
  42. 		k = 2 * i - 1;
  43. 		while (k > 1) {
  44. 			v = pr[pl[k]];
  45. 			upd(pl[k], 1);
  46. 			k /= v;
  47. 		}
  48. 		k = i + 1;
  49. 		while (k > 1) {
  50. 			v = pr[pl[k]];
  51. 			upd(pl[k], -1);
  52. 			k /= v;
  53. 		}
  54. 		res += d[1];
  55. 		if (res >= m) res %= m;
  56. 	}
  57. 	printf("%lld", res);
  58. }
Success #stdin #stdout 0s 5724KB
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https://ideone.com/xUypN1
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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