Problem	area
User	gthinh
Submission Time	2026-01-26 10:11:15
Score	0
Max Time	N/A
Max Memory	N/A

Compile Error

area.cpp: In function ‘std::string add(std::string, std::string)’:
area.cpp:16:17: error: ‘sum’ was not declared in this scope
16 | a[i] = (sum%10)+'0';
| ^~~