#include <cstdio>
#include <cstring>
#include <cctype>

int main(void){
	while(8){
		int N; scanf(" %d ", &N);
		if (!N) break;

		char M[10047]; fgets(M, 10047, stdin);
		char R[10047]; int cnt = 0;
		memset(R, 0, sizeof(R));
		char Res[10047]; int d = 0, pos = 0, pom = 0;
		memset(Res, 0, sizeof(Res));

		for (unsigned i = 0; i < strlen(M); i++)
			if(isalpha(M[i])) R[cnt++] = M[i] <= 'Z' ? M[i] : (M[i] - 'a' + 'A');

		while(d < cnt){
				if (pos >= cnt) pos = ++pom;
				Res[pos] = R[d];
				pos += N;
				d++;
		}

		printf("%s\n", Res);
	}
	return 0;
}