#include<stdio.h>
 
int main(void)
{
    int student;
    int num;
    int i;
 
    while (scanf("%d", &num) != EOF){
        student = 1;
 
        for (i = 1; i < num; ++i){
            if (student < 39){
                student++;
            }
            else if (student == 39){
                student = 1;
            }
        }
         
        printf("3C%02d\n", student);
    }
}