Compilare: user.cpp: In function ‘void write_output()’: user.cpp:102: warning: comparison between signed and unsigned integer expressions user.cpp:107: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘bool find_next(int&, int&)’: user.cpp:80: warning: ‘x1’ may be used uninitialized in this function user.cpp:80: warning: ‘y1’ may be used uninitialized in this function