metrou.cpp: In function 'void build_chain(int)': metrou.cpp:78: warning: comparison between signed and unsigned integer expressions metrou.cpp:95: warning: comparison between signed and unsigned integer expressions metrou.cpp: In function 'int solve()': metrou.cpp:122: warning: comparison between signed and unsigned integer expressions metrou.cpp:131: warning: comparison between signed and unsigned integer expressions metrou.cpp: In function 'int main()': metrou.cpp:152: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result metrou.cpp:153: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result metrou.cpp:155: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result metrou.cpp:157: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result metrou.cpp:159: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result