Compilare: user.cpp: In function ‘void OpenFiles(int)’: user.cpp:23: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:24: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:27: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘void dfs_sub(int, int)’: user.cpp:46: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void dfs_lant(int, int, int)’: user.cpp:63: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main(int, char**)’: user.cpp:152: warning: comparison between signed and unsigned integer expressions user.cpp:168: warning: comparison between signed and unsigned integer expressions user.cpp:137: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:138: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:141: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:182: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘int lca(int, int)’: user.cpp:82: warning: control reaches end of non-void function