include

include

using namespace std; int main() {

int n,j=0,o=0,s=0;
cin>>n;
for(long long i=pow(10,n-1);i<=pow(10,n)-1;i++)
{
	//cout<<i<<endl;
	o=0;
	j=i;
	while(j>0)
	{
		if(j%10==3)
		  o++;
		j=j/10;
	}
	if(o%2==0)
	  s++;
}
cout<<s;

}

数据库忘加了

号忘加了