Compilare: main.cpp: In function 'int val(std::__cxx11::string, std::__cxx11::string)': main.cpp:12:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < a.size(); ++i) { ~~^~~~~~~~~~ main.cpp:13:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j < b.size(); ++j) { ~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:34:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < v.size() - 1; ++i) { ~~^~~~~~~~~~~~~~