// yukicoder: 238 Mr. K's Another Gift
// 2019.6.8 bal4u

#include <stdio.h>

#if 1
#define gc() getchar_unlocked()
#define pc(c) putchar_unlocked(c)
#else
#define gc() getchar()
#define pc(c) putchar(c)
#endif

int ins(char *s)  // 文字列の入力　スペース以下の文字で入力終了
{
	char *p = s;
	do *s = gc();
	while (*s++ > ' ');
	*--s = 0;
	return s - p;
}

void outs(char *s) { while (*s) pc(*s++); }

int check(char p, char *a, char *b, char q) {
	if (p > 0) {
		if (*b-- != p) return 0;
	} else {
		if (*a++ != q) return 0;
	}
	while (a < b && *a == *b) a++, b--;
	return a >= b;
}

char s[100005];
int main()
{
	int N;
	char c, d, *p, *q;
	
	N = ins(s);
	if (N == 1) pc(*s), pc(*s);
	else {
		p = s, q = s + N - 1;
		while (p < q && *p == *q) p++, q--;
		if (p < q) {
			if (check(*q, p, q, 0))
				c = *q, d = *p, *p = 0, outs(s), pc(c), pc(d), outs(p+1);
			else if (check(0, p, q, *p)) 
				c = *p, d = *q, *q = 0, outs(s), pc(d), pc(c), outs(q+1);
			else outs("NA");
		} else {
			c = s[N/2], s[N/2] = 0, outs(s), pc(c), pc(c), outs(s+N/2+1);
		}
	}
	pc('\n');
	return 0;
}