#include<stdio.h>
#include<ctype.h>
#include<string.h>
#include<stdbool.h>
#define MAX 100
bool isValid(char c)
{
    return isalnum (c)||isspace(c);
}
void removeduplicate(char*str)
{
    bool seen[256]={false};
    int len =strlen(str);
    int writeindex=0;
    for(int readindex=0; readindex<len;++readindex)
    {
        char c=str[readindex];
        if(!seen[(unsigned char)]c)
        {
            seen[(unsigned char)c]=true;
            str[writeindex++]=c;
            
        }
    }
    str[writeindex]='\0';
    }
    int main()
    {
        char input[MAX];
        fgets(input,sizeof(input),stdlin);
        input[strcspn(input,"\n")]=0;
        bool isValidinput=true;
        for(i=0;input[i];i++)
        {
            if(!isvalid(input[i]))
            {
                isValidinput=false;
                break;
                
            }
        }
        if(isvalidinput)
        {
            removeduplicates(input);
            printf("%s\n",input);
        }
        else
        {
            printf("invalid input\n");
            
        }
        return 0;
    }
}