#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
char s[101];
int seen[256]={0};
int i;
scanf("%[^\n]",s);
for(i=0;s[i]!='\0';i++)
{
if(!salnum(s[i])&& s[i]!=' '){
printf("Invalid input\n");
return 0;
}
}
for(i=0;s[i]!='\0';i++){
if(isalnum(s[i])&&!seen[(unsigned char)s[i]]0{
printf("%c",s[i]);
seen[(unsigned char)s[i]]=1;
}
}
printf("\n");
return 0;
}