Write a program to count the number of days between two dates.
The two dates are given as strings, their format is YYYY-MM-DD as shown in the examples.
Example 1:
Input: date1 = "2019-06-29", date2 = "2019-06-30" Output: 1
Example 2:
Input: date1 = "2020-01-15", date2 = "2019-12-31" Output: 15
Constraints:
- The given dates are valid dates between the years
1971and2100.