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