#include<stdio.h>
#include<string.h>
#include<ctype.h>

int main()
{
    char str[101];
    int seen[256] = {0};
    char result[101];
    int i, j = 0, invalid = 0;
    
    fgets(str,sizeof(str), stdin);
    str[strcspn(str,"\n")] = '\0';
    
    for(i=0;str[i] !='\0'; i++)
    {
        if(!(isalnum(str[i]) || str[i] == ''))
        {
            invalid=1;
            break;
        }
    }
    if(invalid)
    {
        printf("Invalid input");
        return 0;
    }
    for(i=0;str[i] !='\0'; i++)
    {
        char lower = tolower(str[i]);
        if(!seen[(unsigned char)lower])
        {
            seen[(unsigned char)lower]=1;
        }
    }
    result[j]='\0';
    
    printf("%s", re)
}