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