Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	table := [6][5]string{
		{"a", "b", "c", "d", "e"},
		{"f", "g", "h", "i", "j"},
		{"k", "l", "m", "n", "o"},
		{"p", "q", "r", "s", "t"},
		{"u", "v", "w", "x", "y"},
		{"z", ".", "?", "!", " "},
	}
	for scanner.Scan() {
		input := strings.Split(scanner.Text(), "")
		if len(input)%2 != 0 {
			fmt.Println("NA")
			continue
		}
		ret := make([]string, 0)
		for i := 0; i < len(input); i += 2 {
			row, _ := strconv.Atoi(input[i])
			col, _ := strconv.Atoi(input[i+1])
			ret = append(ret, table[row-1][col-1])
		}
		fmt.Println(strings.Join(ret, ""))
	}
}

C++: #include<iostream>
#include<vector>
#include<string>
using namespace std;

int main() {
	string a;
	while (cin >> a) {
	k:;
		if (a.length() % 2) { cout << "NA" << endl; continue;}
		for (int b = 0; b < a.length(); b += 2) {
			if (a[b]<'1' || a[b]>'6' || a[b + 1]<'1' || a[b + 1]>'5') { cout << "NA" << endl; goto k; }
			int s = (a[b] - 49) * 5 + (a[b + 1] - 49);
			if ((s + 97) < '{')	cout << (char)(s + 97);
			else {
				switch (s + 97) {
				case 123:cout << '.'; break;
				case 124:cout << '?'; break;
				case 125:cout << '!'; break;
				case 126:cout << ' '; break;
				}
			}
		}
		cout << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
string s[]={"afkpuz","bglqv.","chmrw?","dinsx!","ejoty "};
int main(){string ss;while(cin>>ss){
if(ss.size()%2==1){cout<<"NA"<<endl;continue;}
bool b=1;string ans="";for(int i=0;i<ss.size()-1;i+=2){
if(!('1'<=ss[i+1]&&ss[i+1]<='5')||!('1'<=ss[i]&&ss[i]<='6')){b=0; break;}
ans+=s[in[i+1]-'0'-1][in[i]-'0'-1];}
if(b)cout<<ans<<endl;else cout<<"NA"<<endl;
}}

C++: /*
	0127:Pocket Pager Input
*/
#include	<iostream>
#include	<string>

using namespace std;

const char WORDS[30] = "abcdefghijklmnopqrstuvwxyz.?! ";

int main(void) {
	char WORDSET[6][5];
	int w = 0;
	
	for(int i = 0; i < 6; i++) {
		for(int j = 0; j < 5; j++) {
			WORDSET[i][j] = WORDS[w];
			w++;
		}
	}
	
	while(1) {
		string str;
		string ans;
		bool fl = true;
		
		cin >> str;
		
		if( cin.eof() ) { break; }
			else if( (int)str.size() % 2 != 0 ) { cout << "NA" << endl; continue; }
		string::iterator it = str.begin();
		while( it != str.end() ) {
			int a, b;
			
			a = *it - '0' - 1;
			it++;
			b = *it - '0' - 1;
			it++;
			
			if(0 <= a && a < 6 && 0 <= b && b < 5) {
				ans += WORDSET[a][b];
			} else {
				fl = false;
				break;
			}
		}
		if(fl) {
			cout << ans << endl;
		} else {
			cout << "NA" << endl;
		}
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

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

int main(){
	
	bool checker;
	
	string str;
	
	while(true){
		cin >> str;
		if(cin.eof()){
			break;
		}
		
		checker = false;
		
		for(int i = 0; i < str.size(); i++){
			if(str[i] < '1' || str[i] > '6'){
				printf("NA\n");
				checker = true;
				break;
			}
		}
		
		if(checker){
			continue;
		}
		
		if(str.size() % 2 != 0){
			printf("NA\n");
			continue;
		}
		for(int i = 0; i < str.size(); i += 2){
			if(str[i + 1] - '0' - 1 >= 5){
				printf("NA\n");
				checker = true;
				break;
			}
		}
		
		if(checker){
			continue;
		}
		
		for(int i = 0; i < str.size(); i += 2){
			printf("%c", c[str[i] - '0' - 1][str[i + 1] - '0' - 1]);
		}
		printf("\n");
	}
	
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <string>
using namespace std;

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

int main() {
  string s;
  while(cin >> s) {
    if(s.size()%2) cout << "NA" << endl;
    else {
      for(int i = 0; i < s.size(); i += 2) {
        printf("%c", index[s[i]-'1'][s[i+1]-'1']);
      }
      cout << endl;
    }
  }
}

C++: #include<iostream>
using namespace std;
int main(){
    char a[7][7] = {"","*abcde","*fghij","*klmno","*pqrst","*uvwxy","*z.?! "};
    string s;
    while(cin>>s){
        if(s.size()%2==1)cout<<"NA"<<endl;
        else{
            for(int i=0;i<s.size();i+=2){
                cout<<a[s[i]-48][s[i+1]-48];

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

C++: #include <iostream>
#include <string>
#include <cstdlib>
using namespace std;

int main(){
	int x,y,f;
	string str;
	const char *table[] = {"abcde","fghij","klmno","pqrst","uvwxy","z.?! "};
	while(cin >> str){
		string t,tmp;
		f = 1;
		if(str.size() % 2 == 0){
			for(int i = 0;i < str.size();i += 2){
				tmp = str[i];
				x = atoi(tmp.c_str()) - 1;
				tmp = str[i+1];
				y = atoi(tmp.c_str()) - 1;
				if(x > 5 || y > 4 || x == 0 || y == 0){
					cout << "NA" << endl;
					f = 0;
					break;
				}
				if(f) t += table[x][y];
			}
			if(f) cout << t << endl;
		}
		else{
			cout << "NA" << endl;
		}
	}
	return 0;
}

C++: #include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <deque>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <functional>
#include <utility>
#include <algorithm>
#include <numeric>
#include <typeinfo>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <ctime>

using namespace std;

#define dump(n) cout<<"# "<<#n<<"="<<(n)<<endl
#define debug(n) cout<<__FILE__<<","<<__LINE__<<": #"<<#n<<"="<<(n)<<endl
#define repi(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,n) repi(i,0,n)
#define iter(c) __typeof((c).begin())
#define foreach(i,c) for(iter(c) i=(c).begin();i!=(c).end();i++)
#define allof(c) (c).begin(),(c).end()
#define mp make_pair

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int,int> pii;

string solve(string s)
{
	char table[6][6]={
		"abcde",
		"fghij",
		"klmno",
		"pqrst",
		"uvwxy",
		"z.?! ",
	};
	if(s.size()&1){
		return "NA";
	}
	else{
		string res;
		for(int k=0;k<s.size();k+=2){
			int i=s[k]-'1';
			int j=s[k+1]-'1';
			if(i<0 || 6<=i || j<0 || 5<=j)
				return "NA";
			res+=table[i][j];
		}
		return res;
	}
}

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

C++: /*
	0127:Pocket Pager Input
*/
#include	<iostream>
#include	<string>

using namespace std;

const char WORDS[30] = "abcdefghijklmnopqrstuvwxyz.?! ";

int main(void) {
	char WORDSET[6][5];
	int w = 0;
	
	for(int i = 0; i < 6; i++) {
		for(int j = 0; j < 5; j++) {
			WORDSET[i][j] = WORDS[w];
			w++;
		}
	}
	
	while(1) {
		string str;
		string ans;
		bool fl = true;
		
		cin >> str;
		
		if( cin.eof() ) { break; }
			else if( (int)str.size() % 2 != 0 ) { cout << "NA" << endl; continue; }
		string::iterator it = str.begin();
		while( it != str.end() ) {
			int a, b;
			
			a = *it - '0' - 1;
			it++;
			b = *it - '0' - 1;
			it++;
			
			if(0 <= a && a < 6 && 0 <= b && b < 5) {
				ans += WORDSET[a][b];
			} else {
				fl = false;
				break;
			}
		}
		if(fl) {
			cout << ans << endl;
		} else {
			cout << "NA" << endl;
		}
	}
	return 0;
}