Well Order Numbers of Given Length in C++

A number is called Well Order if every digit is greater than previous one(Eg: 238 is well Order as 2<3<8 but 132 is not). Given length of a number, Find all well ordered numbers of Given Length

Input:  Length of number
Output : Well Ordered numbers of given length



#include <iostream>
#include <vector>
#include <cmath>

using namespace std;
int p;
void PrintNum ( int prefix,int s, int n )
{
    if ( n==0 && prefix>=pow ( 10.0, p-1 ) )
    {
        cout<< prefix<<"\n";
    }
    else
    {
        for ( int i=s; i<10; i++ )
        {
            PrintNum ( 10*prefix+i, i+1, n-1 );
        }
    }
}
int main()
{
    cin>>p;
    PrintNum ( 0,0,p );
    getchar();

}

Please comment if you find anything incorrect or have any inputs to improve the code.