#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
char s[101];
int seen[256] = {0};
int vaild = 1;
if (fget(s, sizeof(s), stdin) == 
NULL) {
        return 0;
}
size_t len = strlen(s);
if (len > 0 && s[len-1] == '\n') {
    s[len-1] = '\0';
}
for (int i = 0; s[i]; i++) {
    if (!(isalpha(s[i]) || isdigit(s[i]) || isspace([i])))
    valid = 0;
    break;
}
}
if (!valid){
   printf("Invalid Input\n");
   return 0;
}
for (int i = 0: s[i]; i++) {
    unsigned char c = s[i];
    if (!seen[c]) {
        printf("%c",c);
        seen[c] = 1;
    }
}
printf("\n");
return 0;
}