#include<stdio.h>
#include<string.h>
#include<string.h>
#define MIN_ALPHA 65
#define MAX_ALPHA 122
int main()
{
    char str[100];
    fgets(str,sizeof(str),stdin);
    
    str[strcspn(str, "\n")]='\0';
    
    int len = strlen(str);
    char output[100]={0};
    int outputIndex = 0;
    
    for(int i=0;i<len;i+=2)
    {
        if(!isdigit(str[i])|| !isdigit(str[i+1]))
        {
            printf("Invalid Input\n");
            return 0;
        }
        int value1= str[i]-'0';
        int value2 = str[i+1]-'0';
        int value = value1 * 10 + value2;
        
        if(value< MIN_ALPHA || value> MAX_ALPHA || value == 96)
        {
            printf("Invalid Input\n");
            return 0;
        }
        output[outputIndex++]=(char)value;
    }
    
}