#include<stdio.h>

int main(){
    char s[101];
    int freq[256];
    int valid;
    char c,lc;
    int i ;
    for( i = 0; i < 256; i++){
        freq[i] = 0;
    }
    valid = 1;
    scanf("%[^\n]",s);
    for(i = 0; s[i] != '\0'; i++){
        c = s[i];
        if(!(c >= 'A' && c <= 'Z' || (c>= 'a' && c<= 'z') || (c>= '0' && c<= '9')|| c ==' ')
     {
         valid = 0;
         break;
     }   
    if(!valid) {
        printf("Invalid input");
        return 0;
    }
    for (int i = 0; s[i] != '\0'; i++){
        
        c = s[i];
        if(c ==' ') continue;
        if(c >= 'A' && c <= 'Z'){
            lc = c+('a' - 'A');
        }else
        {
            lc = c;
        }
            if(freq[(int)lc] == 0){
            printf("%c" , &c);
            freq[(int)lc] = 1;
        }
    }
    return 0;
}