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