C :

#include<stdio.h>
int main()
{
	int a,b;
	char c;
	scanf("%c",&c);
	if(c>=48&&c<=57)
	{
		a=c-48;
		printf("%d\n",a);
	}
	else printf("#\n");
}

C++ :

#include<iostream>
using namespace std;
int main()
{
	int a;
	char b;
	cin>>b;
	while (cin)
	{
		if (b>='0'&&b<='9')
		{	a=b-'0';
		    cout<<a<<endl;
		}
		else 
			cout<<"#回车"<<endl;
		cin>>b;
	}
	return 0;
}