#include<stdio.h>
#include<ctype.h>
int main()
{
    char s[101],seen[256]={0};
    int i;
    fgets(s,100,stdin);
    for(i-0;s[i];i++)
    {
        if(!(isalnum(s[i])||s[i]==' '))
        {
            printf("Invalid input");
        }
        if(!seen[(unsigned char)s[i]])
        {
            printf("c",s[i]);
            seen[(unsigned char)s[i]]=1;
        }
    }
}