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

int main(int argc, char **argv) {
	int cipher;
	char *msg = (char *)malloc(10001 * sizeof(char));
	char *enc;
	char c;
	char diff = 'A' - 'a';
	int len;
	char *ence;
	char *encp;
	int first = 1;
	while(1) {
		scanf("%d", &cipher);
		if(cipher == 0) break;
		
		char *msgp = msg;
		char *msgp2 = msg;
		getchar();
		c = getchar();
		while(c != '\n') {
			if(c >= 'a' && c <= 'z') *(msgp++) = c + diff;
			else if(c >= 'A' && c <= 'Z') *(msgp++) = c;

			c = getchar();
		}

		len = msgp - msg;
		enc = (char *) calloc(len + 1, sizeof(char));
		ence = enc + len;
		encp = enc;
		int i = 0;

		for(; msgp2 < msgp; msgp2++) {
			//putchar(*msgp2);
			*encp = *msgp2;
			encp += cipher;

			if(encp >= ence) {
				i++;
				encp = enc + i;
			}
		}
		//if(!first) printf("\n");
		printf("%s\n", enc);

		first = 0;
	}

	return 0;
}