Compilare: user.cpp: In function ‘int main()’: user.cpp:40:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v[1].size(); i++) ^ user.cpp:63:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v[get<1>(a)].size(); i++) ^ user.cpp:60:13: warning: unused variable ‘nx’ [-Wunused-variable] int nx; ^