P1919 [Template] High-Precision Multiplication | A*B Problem Enhanced

The testdata has been strengthened. Please use FFT or divide-and-conquer multiplication.

Given two positive integers $a, b$, compute $a \times b$.

The first line contains a positive integer representing $a$. The second line contains a positive integer representing $b$.

Output a single line containing the integer answer.

[Constraints] $1 \le a, b \le 10^{1000000}$ Some constant-factor optimization may be required. The testdata was remade by NaCly_Fish. Translated by ChatGPT 5