spider.cpp: In function 'int main()': spider.cpp:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result spider.cpp:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result spider.cpp:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result spider.cpp:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result spider.cpp: In function 'int calc(int, int, int)': spider.cpp:27: warning: control reaches end of non-void function spider.cpp:8: warning: 'p' may be used uninitialized in this function spider.cpp:8: warning: 'nx' may be used uninitialized in this function spider.cpp:8: warning: 'ny' may be used uninitialized in this function spider.cpp: In function 'int main()': spider.cpp:32: warning: 'si' may be used uninitialized in this function spider.cpp:32: warning: 'sj' may be used uninitialized in this function spider.cpp:32: warning: 'p' may be used uninitialized in this function spider.cpp:32: warning: 'nx' may be used uninitialized in this function spider.cpp:32: warning: 'ny' may be used uninitialized in this function