#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[100];
    scanf("%s",s);
    
    int len=strlen(s);
    if(len%2!=0){
        printf("Invalid Input");
        return 0;
    }
    char result[100];
    int k=0;
    for(int i=0;i<len;i+=2){
        char pair[3];
        pair[0]=s[i];
        pair[1]=s[i+1];
        pair[2]='\0';
        int ascii_val;
        sscanf(pair,"%d",&ascii_val);
        char ch=(char)ascii_val;
        if(isalpha(ch)){
            result[k++]=ch;
        }
        else{
            printf("Invalid Input");
            re
        }
    }
}