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

#define MAX_DIG 2000
char * numbers = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

char ret1[MAX_DIG+1] , ret2[MAX_DIG+1], ret3 [(2 * MAX_DIG)+1];

int main (void) {
 int zaklad;
 char * pos1, *pos2, *pos3;
 int val1, val2, val3;
 int prenos;
 while (1) {
	 prenos=0;
   scanf("%d", &zaklad);
	 if (zaklad == 0 ) {
	   return 0;
	 }
	 scanf("%s %s", ret1, ret2);
   if ( zaklad == 1 ) {
		 printf("%s%s\n", ret1, ret2);
		 continue;
	 } else {
		 val3=0;
		 pos1=ret1+(strlen(ret1)-1); 
		 pos2=ret2+(strlen(ret2)-1); 
		 pos3=ret3 + 2 * MAX_DIG;
		 while (pos1 >= ret1 || pos2 >= ret2) {
       if (pos1 >= ret1) {
			  val1=strchr(numbers, *pos1) - numbers;
				pos1--;
			 } else {
				val1 = 0;
			 }
       if (pos2 >= ret2) {
			  val2=strchr(numbers, *pos2) - numbers;
				pos2--;
			 } else {
				val2 = 0;
			 }
			 val3 = val1 + val2 + prenos;
			 prenos = 0;
			 while (val3 >= zaklad) {
   		   val3 -= zaklad;
				 prenos++;
			 }
			 /*fprintf(stderr, "A=%c, B=%c, TRANS=%i, val=%i\n", 
											  *(pos1+1), *(pos2+1), prenos, val3 );*/
			 *pos3 = numbers [val3];
			 pos3--;
		 }		 
		 if (prenos) {
				*pos3 = numbers [prenos];
		 } else {
				pos3++;
		 }
		 printf("%s\n", pos3);		
	 }  
 }
}