#include "bits/stdc++.h"

using namespace std;

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

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back

int main(){
    char ch[10][10]={ {'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','.','?','!',' '} };
    string s;
    while(cin>>s){
        int len=s.size();
        string ans="";
        
        try{
            if(len%2==1)throw 1;
            for(int i=0;i<len;i+=2){
                int a,b;
                if(s[i]<'1' || '6'<s[i] || s[i+1]<'1' || '5'<s[i+1] )throw 1;
                a=s[i]-'0'-1;
                b=s[i+1]-'0'-1;
            
                ans+=ch[a][b];
            }
        }catch(int a){
            cout<<"NA"<<endl;
            goto next;
        }
        cout<<ans<<endl;
        next:;
    }
}