C/C++ :: Count Number Of Digits In Long Variable - While Loop

So I have been given and as part of the solution I need to count the number of digits in a long long variable. To do this I use a while loop, but it is behaving strangely. Here is the code.

#include <stdio.h>
#include <cs50.h>
#include <math.h>
int main (void) {
printf("What is the card number?
");
long long card = GetLongLong();
if(card <= 0)

[Code] .....

When I execute the program it asked for the number, but then nothing happens. Of course, my first instinct was that the program was caught in an infinite loop somehow, but could not figure out how. I commented out the while loop and the program completed (albeit returning the incorrect value), so I was further convinced that there was an infinite loop that I was not seeing. I ran the program throug gdb. Strangely, the program did not loop infinitely, instead it got to line 16 [while(card1 > 0] and then just stopped, it was not executing the next line of code at all.