#include<stdio.h>
#include<ctype.h>
int main(){
    char s[101],o[101]={0},v[256]={0};int
i,k=0;
    fgets(s,101,stdin);
    for(i=0;s[i];i++){
        if(!isalnum(s[i]) && s[i]!='0')
{printf("Invalid input");return 0;}
        if(!v[(unsigned char)s[i]]), v[(unsigned char)s[i]]=1, o[k++]=s[i];
    }
    printf("%s",o);
    
    
}