4{b}

#include<stdio.h>
int main()
{
    int n,r,sum=0,temp;
    scanf("%d",&n);
    temp=n;
    while(temp!=0)
    {
        r=temp%10;
        if(r%2!=0){
        sum=sum*10+r;}
        temp=temp/10;
    }
    int r1,s=0,temp1;
    temp1=sum;
    while(temp1!=0)
    {
        r1=temp1%10;
        s=s*10+r1;
        temp1=temp1/10;
    }
    printf("%d",s);
    return 0;
}