1.a

#include <iostream>
using namespace std;
int main ()
{
    int n, p, c, u=1;
    cin>>n;
    p=0;
    while (n%10!=0)
    {
        c=n%10;
        if (c<=5)
        {
            p=p+c*u;
            u=u*10;
        }
        n=n/10;
    }
    cout<<p;
    return 0;
}