Compilare: main.cpp: In function 'std::__cxx11::string rez(std::__cxx11::string, std::__cxx11::string, std::__cxx11::string, std::__cxx11::string, std::__cxx11::string)': main.cpp:24:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < a.size()) cr += a[i] - '0'; ~~^~~~~~~~~~ main.cpp:25:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < b.size()) cr += b[i] - '0'; ~~^~~~~~~~~~ main.cpp:26:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < c.size()) cr += c[i] - '0'; ~~^~~~~~~~~~ main.cpp:27:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < d.size()) cr += d[i] - '0'; ~~^~~~~~~~~~ main.cpp:28:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < e.size()) cr += e[i] - '0'; ~~^~~~~~~~~~