In documentation terminology, indentation means the space from margin to the begin of characters in a line.
Python uses indentation. In your code, While is a condition, all the block of code to be executed for true, must start at same position from the margin, must be farther away from margin than that of the condition.
I too faced this error.
Example:
if __name__ == '__main__':
a = int(input())
b = int(input())
if a>=1 and a<=10000000000 and b>=1 and b<=10000000000:
print(a+b)
print(a-b)
print(a*b)
will throw "IndentationError: expected an indented block (solution.py, line 5)"
Fix:
if __name__ == '__main__':
a = int(input())
b = int(input())
if a>=1 and a<=10000000000 and b>=1 and b<=10000000000:
print(a+b)
print(a-b)
print(a*b)