balls.cpp: In function 'std::string Elim(std::string)': balls.cpp:27: warning: comparison between signed and unsigned integer expressions balls.cpp: In function 'void Solve()': balls.cpp:70: warning: comparison between signed and unsigned integer expressions balls.cpp:86: warning: comparison between signed and unsigned integer expressions balls.cpp:93: warning: comparison between signed and unsigned integer expressions balls.cpp:98: warning: comparison between signed and unsigned integer expressions