What will be the output of the following C++ code?

#include <iostream>
using namespace std;
void PrintSequence(int StopNum)
{
    int Num;
    Num = 1;
    while (true) 
    {
        if (Num >= StopNum)
            throw Num;
        cout << Num;
        Num++;
    }
}
int main(void)
{
    try 
    {
        PrintSequence(20);
    }
    catch(int ExNum)
    {
        cout << "Caught an exception with value: " << ExNum;
    }
    return 0;
}