#include <iostream>
#include <string>
#include <cstring>
using namespace std;

int main(){
char moji[5][7] = {{'a','f','k','p','u','z'},{'b','g','l','q','v','.'},{'c','h','m','r','w','?'},{'d','i','n','s','x','!'},{'e','j','o','t','y',' '}};
    string s;
    char ans[1000];
    bool judge;
    while(cin >> s){
        memset(ans,0,sizeof(ans));
        judge = false;
        for(int i=0,j=0;i<s.size();i+=2,j++){
            if(s.size() % 2 != 0) {
                cout << "NA" << endl;
                judge = true;
                break;
            }
            if(!(s[i] >= '1' && s[i] <= '6' && s[i+1] >= '1' && s[i+1] <= '5')){
                cout << "NA" << endl;
                judge = true;
                break;
            }
            ans[j] =  moji[(s[i+1]%'0')-1][(s[i]%'0')-1];
        }
        if(!judge) cout << ans << endl;
    }
}