#include<stdio.h>
int main(void)
{
int a,b,c,x;
b=39;
scanf("%d",&a);
	if(a<b)
	{
		b=b-a;
	}
	else
	{
		x=a%b;
		if(a%b==0)
		{
			x=39;
		}
		b=0;
		b=b+x;
	}
	if(b<10)
	{
		printf("3C0%d\n",b);
	}
	else
	{
	printf("3C%d\n",b);
	}
return 0;
}