Compilare: user.cpp: In function ‘void solve()’: user.cpp:55:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == lena) { ^ user.cpp: In function ‘void input()’: user.cpp:16:25: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%s", a); ^ user.cpp:17:25: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%s", b); ^