sudoku1.cpp: In function 'int main()': sudoku1.cpp:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sudoku1.cpp:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sudoku1.cpp:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sudoku1.cpp: In function 'int calc(int, int, int)': sudoku1.cpp:30: warning: control reaches end of non-void function