#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main() {
    char s[101],res[101];
    int seen[256]= {0}; 
    int i=0;k= 0;
    unsigned char ch,lower;
    while((ch = getchar()) != '\n' && ch != EOF && i < 100)
    s[i++] = ch;
    s[i] = '\0';
    
    for( i = 0; s[i] !='\0'; i++) {
        ch = s[i];
        if(!(isalnum(ch) || ch == ' ')) {
         printf("Invalid input");
            return 0;
        }
        lower =  tolower(ch);
    if(!seen[lower]) {
        res[k++] = s[i];
        seen[lower] = 1;
    }
}
res[k]='\0';
printf("%s",res);
return 0;
}