// editor1
#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(void)
{
    char s[201];
    if(!fgets(s,sizeof(s),stdin))
    return 0;
}
int n=strlen(s);
if(n>0&&s[n-1]=='\n'){
    s[n-1]='\0';
    n--;
}
for(size_t int i =0;i<n;i++)
{
   if(!(isalnum((unsigned char)s[i]|| s[i]==' '))
   {
       printf("Invalid input");
       return 0;
   }
    }
    int freq[256]={0};
    for(int i=0;i<n;i++){
        freq[(unsigned char ch)s[i}];
    }
    for (int i=0;;i<n;i++){
        if(freq[(unsigned char)s[i]]==1){
            putchar(s[i]);
        }
    }
    return 0;
    }