#ifdef LOCAL111
#else
	#define NDEBUG
#endif
#include <bits/stdc++.h>
const int INF = 1e9;
using namespace std;
template<typename T, typename U> ostream& operator<< (ostream& os, const pair<T,U>& p) { cout << '(' << p.first << ' ' << p.second << ')'; return os; }

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RBP(i,a) for(auto& i : a)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
	template<typename T> void dpite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
#else
	#define DEBUG(x) true
	template<typename T> void dpite(T a, T b){ return; }
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
#define rangej(a,b,c) ((a) <= (c) and (c) < (b))
#define rrangej(b,c) rangej(0,b,c)
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<int,int> P;
typedef pair<LL,LL> LP;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

bool check(string& s){
	bool res = true;
	REP(i,SZ(s)/2){
		if(s[i] == 'z'+1){
			s[i] = s[SZ(s)-1-i];
		}
		if(s[SZ(s)-1-i] == 'z'+1){
			s[SZ(s)-1-i] = s[i];
		}
		if(s[i] != s[SZ(s)-1-i]) res = false;
	}
	return res;
}

int main()
{
	ios_init();
	string s;
	while(cin >> s){
		int po = -1;
		REP(i,SZ(s)){
			if(s[i] != s[SZ(s)-1-i]){
				po = i;
				break;
			}
		}
		if(po == -1){
			if(SZ(s)%2 == 0){
				s.insert(SZ(s)/2,"a");
			}else{
				s.insert((SZ(s)+1)/2,s.substr(SZ(s)/2,1));
			}
			cout << s << endl;
		}else{
			string ans = "NA";
			string t(SZ(s)+1,'z'+1);
			int p = 0;
			int rp = 0;
			while(p < SZ(t)){
				if(p == po) p++;
				else{
					t[p] = s[rp];
					p++;
					rp++;
				}
			}
			if(check(t)){
				ans = t;
			}
			t = string(SZ(s)+1,'z'+1);
			p = 0;
			rp = 0;
			while(p < SZ(t)){
				if(p == SZ(s)-po) p++;
				else{
					t[p] = s[rp];
					p++;
					rp++;
				}
			}
			if(check(t)){
				ans = t;
			}
			cout << ans << endl;
		}
	}
	return 0;
}