#include
#include
#include
using namespace std;
string a,b;
int main()
{ cin>>a>>b;
if(a.find(b)!=a.npos)
{
cout<<b<<" is substring of "<<a<<"\n";
}
else if(b.find(a)!=b.npos)
{
cout<<a<<" is substring of "<<b<<"\n";
}
else cout<<"No substring\n";
return 0;
}