Code not working

#1

10^18 is too big to store the answer in an integer array
or char

#2

@kartik-malik It is not too big for character array, you can easily make a string of length 18 what is the issue?

#3

2 test cases failing test case 2 and 4 failing

#4
#5

@kartik-malik there cant be any leading 0s, so if the string is
954, output should be 944 but your output is 44