Compilare: main.cpp: In function 'int main()': main.cpp:35:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < lista[a].size(); i++) ~~^~~~~~~~~~~~~~~~~ main.cpp:42:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < lista[b].size(); j++) ~~^~~~~~~~~~~~~~~~~ main.cpp:32:16: warning: unused variable 'b' [-Wunused-variable] int a, b; ^