// editor4
#include<stdio.h>
#include<ctype.h>
int main()
{
    char s[101];
    if(scanf("%100s",s)!=1)
    return 0;
    for(int i=0;s[i]!='\0';i+=2)
    {
        if(s[i+1]=='\0')
        {
            printf("Invalid Input");;
            return 0;
        }
      if(!isdigit((unsigned char)s[i])||!isdigit((unsigned char)s[i+1]))
        {
            printf("Invalid \nInput");
            return 0;
        }
        int val=(s[i]-'0')*10+(s[i+1]-'0');
      if(!((val>=65 && val<=90) || (val>=9 7&& val<=122)))
        {
            printf("Invalid \nInput");
            return 0;
        }
        printf("%c",(char)val);
    }
    return 0;
}