copaci3.cpp: In function 'void dfs(int)': copaci3.cpp:21: warning: comparison between signed and unsigned integer expressions copaci3.cpp: In function 'int main()': copaci3.cpp:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result copaci3.cpp:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result copaci3.cpp:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result copaci3.cpp:40: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result copaci3.cpp:69: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result copaci3.cpp:52: warning: 'start' may be used uninitialized in this function