#include <vector>
#include <list>
#include <map>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <queue>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <cstdio>
#include <climits>
#include <complex>
#include <cstdint>
#include <tuple>

#define M_PI       3.14159265358979323846

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
inline int readInt() { int x; scanf("%d", &x); return x; }

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<int, PII> TIII;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;

//container util

//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a)*(a))
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,s,n) for(int i=s;i<(int)n;++i)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
struct Edge {
    int to, cost;
    Edge(int to, int cost): to(to), cost(cost) {}
};

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vector<Edge>> AdjList;
AdjList graph;

const int INF = 100000000;

int main() {
    //cout << fixed << setprecision(15);

    map<pair<int, int>, char> mp;

    mp[{1, 1}] = 'a';
    mp[{1, 2}] = 'b';
    mp[{1, 3}] = 'c';
    mp[{1, 4}] = 'd';
    mp[{1, 5}] = 'e';
    mp[{2, 1}] = 'f';
    mp[{2, 2}] = 'g';
    mp[{2, 3}] = 'h';
    mp[{2, 4}] = 'i';
    mp[{2, 5}] = 'j';
    mp[{3, 1}] = 'k';
    mp[{3, 2}] = 'l';
    mp[{3, 3}] = 'm';
    mp[{3, 4}] = 'n';
    mp[{3, 5}] = 'o';
    mp[{4, 1}] = 'p';
    mp[{4, 2}] = 'q';
    mp[{4, 3}] = 'r';
    mp[{4, 4}] = 's';
    mp[{4, 5}] = 't';
    mp[{5, 1}] = 'u';
    mp[{5, 2}] = 'v';
    mp[{5, 3}] = 'w';
    mp[{5, 4}] = 'x';
    mp[{5, 5}] = 'y';
    mp[{6, 1}] = 'z';
    mp[{6, 2}] = '.';
    mp[{6, 3}] = '?';
    mp[{6, 4}] = '!';
    mp[{6, 5}] = ' ';


    string s;
    while(cin >> s){
        if((int)s.size()%2==1) {
            cout << "NA" << endl;
            continue;
        }
        bool f = false;
        for(int i=0; i<s.size(); i+=2){
            if(mp.find({s[i]-'0', s[i+1]-'0'}) == mp.end()) f = true;
        }
        if(f){
            cout << "NA" << endl;
            continue;
        }
        for(int i=0; i<s.size(); i+=2){
            
            cout << mp[{s[i]-'0', s[i+1]-'0'}];
        }
        cout << endl;
    }
    return 0;
}


Measured memory_bytes: 3020