red.cpp: In function 'std::string produs(std::string, std::string)': red.cpp:16: warning: comparison between signed and unsigned integer expressions red.cpp:17: warning: comparison between signed and unsigned integer expressions red.cpp:22: warning: comparison between signed and unsigned integer expressions red.cpp: In function 'std::string suma(std::string, std::string)': red.cpp:44: warning: comparison between signed and unsigned integer expressions red.cpp: In function 'std::string big_div(std::string, int)': red.cpp:58: warning: comparison between signed and unsigned integer expressions red.cpp:64: warning: comparison between signed and unsigned integer expressions red.cpp:65: warning: comparison between signed and unsigned integer expressions