#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define UB upper_bound
#define LB lower_bound
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

string solve(string s) {
	int n = s.size();
	string t = s;
	reverse(ALL(t));
	if(s == t) {
		s.insert(n / 2, 1, s[n / 2]);
		return s;
	}
	
	int l = 0, r = n - 1;
	while(s[l] == t[l]) { l++; }
	while(s[r] == t[r]) { r--; }
	
	bool flag = true;
	incID(i, l, r) {
		if(s[i] != t[i + 1]) { flag = false; }
	}
	if(flag) {
		s.insert(l, 1, t[l]);
		return s;
	}
	
	flag = true;
	incID(i, l, r) {
		if(s[i + 1] != t[i]) { flag = false; }
	}
	if(flag) {
		s.insert(r + 1, 1, t[r]);
		return s;
	}
	
	return "NA";
}

int main() {
	string s;
	cin >> s;
	
	cout << solve(s) << endl;
	
	return 0;
}