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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Ideone
  6. {
  7.     static int mod=10000007;
  8.     static int max=10000;
  9.     static long fact[]=new long[max+1];
  10.     static long ifact[]=new long[max+1];
  11.  
  12.     static long power(long base,int exp,int mod)
  13.     {
  14.         long result=1;
  15.         while(exp>0)
  16.         {
  17.             if(exp%2==1)
  18.             result=(result*base)%mod;
  19.             base=(base*base)%mod;
  20.             exp/=2;
  21.         }
  22.         return result;
  23.     }
  24.  
  25.     public static void factorial()
  26.     {
  27.         fact[0]=1L;
  28.         for(int i=1;i<=max;i++)
  29.         {
  30.             fact[i]=(fact[i-1]*i)%mod;
  31.         }
  32.         ifact[0]=1L;
  33.         ifact[max]=power(fact[max],mod-2,mod);
  34.         for(int i=max-1;i>=1;i--)
  35.         ifact[i]=(ifact[i+1]*(i+1))%mod;
  36.     }
  37.  
  38.     static long ncr(int n,int r)
  39.     {
  40.         if(n<r||r<0)return 0;
  41.         long res=fact[n];
  42.         res=(res*ifact[r])%mod;
  43.         res=(res*ifact[n-r])%mod;
  44.         return res;
  45.     }
  46.  
  47.     public static void main(String[] args)throws java.lang.Exception
  48.     {
  49.         factorial();
  50.         Scanner sc=new Scanner(System.in);
  51.         int n=sc.nextInt();
  52.         int r=sc.nextInt();
  53.         long ans=ncr(n,r);
  54.         System.out.println(ans);
  55.     }
  56. }
Success #stdin #stdout 0.14s 58696KB
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https://ideone.com/E0GRBd
language:
Java (HotSpot 12)
created:
4 days ago
visibility:
public

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