/*  This Code is Submitted by wywcgs for Problem 1088 on 2005-10-30 at 00:07:58 */ 
#include <cstdio>
#include <cstring>

char word[128];

int encrypt(char);
char decrypt(int);

int main()
{
	char code[128], word[128];
	int k, n;
	int i;

	while(scanf("%d", &k) == 1) {
		if(k == 0) {
			return 0;
		} else {
			scanf("\n");
			gets(code);
			n = strlen(code);
			memset(word, 0, sizeof(word));
			for(i = 0; i < n; i++) {
				word[k*i%n] = decrypt((encrypt(code[i]) + i) % 28);
			}
			printf("%s\n", word);
		}
	}
	
	return 0;
}

int encrypt(char w)
{
	if(w == '_') {
		return 0;
	} else if(w >= 'a' && w <= 'z') {
		return w - 'a' + 1;
	} else {
		return 27;
	}
}
char decrypt(int c)
{
	if(c == 0) {
		return '_';
	} else if(c >= 1 && c <= 26) {
		return c + 'a' - 1;
	} else {
		return '.';
	}
}