#include<iostream>
#include<cctype>
#include<string>
using namespace std;
int main()
{
string s ,result ;
getline(cin,s);
if(s.find('-'))!=string::npos)
{
    cout<<"Invalid input";
    return 0;
}
for(char c:s)
{
    if(isalnum(c))
    result+=c;
}
if (result.empty())
{
    cout<<"Invalid input";
    
}
else
{
    cout<<result;
}
return 0;
}