Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:46:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < l[i].size(); j ++ ) { ^ user.cpp:54:17: warning: unused variable ‘x’ [-Wunused-variable] int x = l[i][(j + 0) % l[i].size()]; ^ user.cpp:55:17: warning: unused variable ‘y’ [-Wunused-variable] int y = l[i][(j + 1) % l[i].size()]; ^