#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[101];
    int count[256] = {0};
    
    
    fgets(s,sizeof(s),stdin);
    
    s[strcspn(s,"\n")] = '\0';
    
    for(int i =0;s[i != '\0'; i++);{
        if(!(isalnum(s[i]) || s[i] == ' ')){
            printf("Invaldi input");
            return 0;
    }
    if(s[i] != ' '){
        count[(unsigned char)s[i]]++;
    }
}

for(int i = 0;s[i] != '\0';i++){
    if(s[i] != ' ' && count[(unsigned char)s[i]] == 1){
        printf("%c",s[i]);
        
    }
}
return 0; 
}