Compilare: user.cpp: In function ‘int pairup(const int&)’: user.cpp:23:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[nod].size(); i++) { ^ user.cpp:32:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[nod].size(); i++) { ^ user.cpp: In function ‘void support(const int&)’: user.cpp:44:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[nod].size(); i++) { ^