rev.cpp: In function 'int main()': rev.cpp:150: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result rev.cpp:151: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result rev.cpp:153: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result rev.cpp:160: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result rev.cpp: In function 'int ans(int)': rev.cpp:122: warning: control reaches end of non-void function