Compilare: main.cpp: In function 'int main()': main.cpp:120:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v[i].size();j++) ~^~~~~~~~~~~~ main.cpp:139:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v2.size();i++) ~^~~~~~~~~~ main.cpp:167:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v2.size();j++) ~^~~~~~~~~~