Compilare: user.cpp: In function ‘bool pairup(int)’: user.cpp:20:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) { ^ user.cpp: In function ‘void aprinde(int)’: user.cpp:33:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ls[x].size(); i++) { ^