Compilare: main.cpp: In function 'void back(int, int)': main.cpp:41:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < elev[i].size(); j++) ~~^~~~~~~~~~~~~~~~ main.cpp:46:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < elev[i].size(); j++) ~~^~~~~~~~~~~~~~~~