#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
	char * s = calloc(1,sizeof(char));
	int i,j;
	for (i=1; i<=3; i++) {
		for(j=1; j<=i; j++) {
			//s = realloc(s, (strlen(s)+1) * sizeof (char));
			int t;
			for (t = strlen(s); t >= 0; t--) {
				s[t+1] = s[t];
			}
            s[0] = j+'0';
		}
	}
	printf("%s\n", s);
	return 0;
}