sudoku1.cpp: In function 'int main()': sudoku1.cpp:16: warning: comparison between signed and unsigned integer expressions sudoku1.cpp:17: warning: comparison between signed and unsigned integer expressions sudoku1.cpp:22: warning: comparison between signed and unsigned integer expressions sudoku1.cpp:41: warning: comparison between signed and unsigned integer expressions sudoku1.cpp:10: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result