Compilare: main.cpp: In function 'std::vector<std::vector<int> > solve(ull)': main.cpp:18:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 18 | for(int i = 0;i < ret.size();++i) | ~~^~~~~~~~~~~~ main.cpp:25:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 25 | for(int i = 0;i < ret.size();++i) | ~~^~~~~~~~~~~~ main.cpp:40:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 40 | for(int i = 0;i < ret.size();++i) | ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:56:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 56 | for(int i = 0;i < ret.size() - 1;++i) | ~~^~~~~~~~~~~~~~~~