#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

int main() {
	int n;
	string s;

	cin >> s;

	int idx_f = 0;
	int idx_b = s.size() - 1;

	bool inserted = false;

	while(idx_f <= idx_b) {
		if (s[idx_f] != s[idx_b]) {
			s.insert(idx_b + 1, 1, s[idx_f]);
			inserted = true;
			break;
		}
		idx_f++;
		idx_b--;
	}

	idx_f = 0;
	idx_b = s.size() - 1;
	while(idx_f <= idx_b) {
		if (s[idx_f] != s[idx_b]) {
			cout << "NA" << endl;
			return 0;
		}
		idx_f++;
		idx_b--;
	}

	if (!inserted) {
		int idx = (s.size() - 1) / 2;
		s.insert(idx + 1, 1, s[idx]);
	}

	cout << s << endl;
	return 0;
}