#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main ()
char s[101],resault [101];
int seen[256] ={0},k = 0;
fgets(s, sizeof(s), stdin);
for(int i = 0; s[i]; i++){
    if(!(isalpha(s[i]) || isdigit(s[i]) || s[i] =='' || s[i]=='\n')){
    printf("Invalid input");
    return 0;
    }
    }
    for(int i = 0; s[i]; i++{
    if(s[i] !='\n'&& !seen[(unsigned char)s[i]]){
    result[k++] = s[i];
    seen[(unsigned char)s[i]] = 1;
    }
    }
    result[k] = '\0';
    printf("%s", result);
    }