Iterative Remainder Calculation for Base Conversion
Check if the input number is zero; if so, return '0'.
Initialize an empty string result to store the base 7 representation.
Check if the input number is negative; if so, set a flag isNegative to true and work with the absolute value of the number.
While the number is greater than zero:
a. Calculate the remainder of the number when divided by 7.
b. Convert the remainder to a string and prepend it to result.
c. Divide the number by 7.