auto.cpp: In function 'bool ok(int)': auto.cpp:19: warning: comparison between signed and unsigned integer expressions auto.cpp: In function 'int main()': auto.cpp:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result auto.cpp:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result auto.cpp:42: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result auto.cpp:45: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result auto.cpp:49: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result