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