Count_good_numbers.txt

class Solution {
public:
    int countGoodNumbers(long long n)
    {
        if(n==0)
            return 0;
        if(n==1)
            return 5;
        long long  evencount,oddcount;
        long long  ans=1,ans1=1;
        if(n&1)
        {
            evencount=((n/2)+1);
            oddcount=(n/2);
        }
        else if(n%2==0)
        {
            evencount=((n)/2);
            oddcount=((n/2));
        }
       
        ans=(power(5,(evencount))%1000000007);
        ans1=(power(4,(oddcount))%1000000007);
      
        return  ((ans*ans1)%1000000007);
    }
   long long power(long long N,long long R)
    {
        if(R==0)
        return 1;
        long long res=power(N,(R/2))%1000000007;
        long long val=((res%1000000007)*(res%1000000007))%1000000007;
        if(R%2!=0)
        {
            val=(((val%1000000007)*(N%1000000007))%1000000007);
        }
      return val;
        
    }
    
};