#include<cstdio>
#include<vector>
#include<algorithm>
#include<cstring>
using namespace std;
int main(){
    char l[6][6]={{0}};
    for(int i=0;i<5;i++){
        for(int j=0;j<5;j++)
            l[i][j]='a'+i*5+j;
    }
    strcpy(l[5],"z.?! ");

    char str[256];
    while(scanf("%s",str)!=EOF){
        if(strlen(str)&1){
            puts("NA");
            continue;
        }
        char ans[128]={0};
        for(int i=0;str[i];i+=2){
            int v1=str[i]-'0'-1,v2=str[i+1]-'0'-1;
            if(v1<0||v1>=6||v2<0||v2>=5){
                puts("NA");
                break;
            }
            ans[i/2]=l[v1][v2];
        }
        printf("%s\n",ans);
    }
    return 0;
}