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