Compilare: user.cpp: In function ‘void prepare(ll)’: user.cpp:26: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:64: warning: unused variable ‘i’ user.cpp:65: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:66: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:72: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result