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  1. /*
  2. * @Author: hungeazy
  3. * @Date:   2024-08-11 15:02:07
  4. * @Last Modified by:   hungeazy
  5. * @Last Modified time: 2024-08-11 15:11:37
  6. */
  7. #include <bits/stdc++.h>
  8. // #pragma GCC optimize("O3")  
  9. // #pragma GCC optimize("unroll-loops")  
  10. // #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")  
  11. using namespace std;
  12. #define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
  13. #define int long long
  14. #define ull unsigned long long
  15. #define sz(x) x.size()
  16. #define sqr(x) (1LL * (x) * (x))
  17. #define all(x) x.begin(), x.end()
  18. #define fill(f,x) memset(f,x,sizeof(f))
  19. #define FOR(i,l,r) for(int i=l;i<=r;i++)
  20. #define FOD(i,r,l) for(int i=r;i>=l;i--)
  21. #define ii pair<int,int>
  22. #define iii pair<int,ii>
  23. #define di pair<ii,ii>
  24. #define vi vector<int>
  25. #define vii vector<ii>
  26. #define mii map<int,int>
  27. #define fi first
  28. #define se second
  29. #define pb push_back
  30. #define MOD 1000000007
  31. #define __lcm(a,b) (1ll * ((a) / __gcd((a), (b))) * (b))
  32. #define YES cout << "YES\n"
  33. #define NO cout << "NO\n"
  34. #define MASK(i) (1LL << (i))
  35. #define c_bit(i) __builtin_popcountll(i)
  36. #define BIT(x,i) ((x) & MASK(i))
  37. #define SET_ON(x,i) ((x) | MASK(i))
  38. #define SET_OFF(x,i) ((x) & ~MASK(i))
  39. #define oo 1e18
  40. #define name ""
  41. #define endl '\n'
  42. #define time() cerr << endl << "-------------Time:" << 1000.0 * clock() / CLOCKS_PER_SEC << "ms.";
  43. template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
  44. template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
  45. const int N = (int)1e6+10, M = (int)1e6;
  46. int m[N],f[N],x,y;
  47.  
  48. int calc(int a, int b)
  49. {
  50. 	if (b == 0) return 1;
  51. 	if (b == 1) return a;
  52. 	int p = calc(a,b/2)%MOD;
  53. 	p = sqr(p)%MOD;
  54. 	if (b&1) (p *= a) %= MOD;
  55. 	return p;
  56. }
  57.  
  58. void init()
  59. {
  60. 	f[0] = 1;
  61. 	FOR(i,1,1e6) f[i] = (f[i-1]*i)%MOD;
  62. 	m[M] = calc(f[M],MOD-2);
  63. 	FOD(i,M-1,0) m[i] = (m[i+1]*(i+1))%MOD;
  64. }
  65.  
  66. int nCr(int n, int k)
  67. {
  68. 	if (n < k) return 0;
  69. 	int res = f[n]%MOD;
  70. 	(res *= m[n-k]) %= MOD;
  71. 	(res *= m[k]) %= MOD;
  72. 	return res;
  73. }
  74.  
  75. namespace hungeazy {
  76.  
  77. 	void solve(void)
  78. 	{
  79. 		int ans = 0;
  80. 		cout << nCr(x-y+1,y);
  81. 	}
  82.  
  83. }
  84.  
  85. signed main()
  86. {
  87.     fast;
  88.     if (fopen(name".inp","r"))
  89.     {
  90.     	freopen(name".inp","r",stdin);
  91.     	freopen(name".out","w",stdout);
  92.     }
  93.     init();
  94.     cin >> x >> y;
  95.     hungeazy::solve();
  96.     time();
  97.     return 0;
  98. }
Success #stdin #stdout #stderr 0.02s 19484KB
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Standard input is empty
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-------------Time:15.815ms.
https://ideone.com/ATyENE
language:
C++14 (gcc 8.3)
created:
9 hours ago
visibility:
public

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