#include<stdio.h>
#include<string.h>
#include<ctype.h>

int main(){
char s[105];
fgets(s,sizeof(s),stdin);
int n = strlen(s);

if(s[n-1]=='\n')
s[n-1]='\0';
n--;
}
int seen[256]={0};
char result[105];
int k=0;

for(int i=0;i<n;i++){
char c=s[i];
if(!(isalnum(c)||c=='')){
printf("Invalid Input");
return 0;
}
if(!seen[(unsigned char)c]){
result[k++]=c;
seen[(unsigned char)]=1;
}
}
result[k]='\0';
printf("%s",result);
return 0;
}