Compilare: main.cpp: In function 'int main()': main.cpp:30:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < m.size(); ++i) ~~^~~~~~~~~~ main.cpp:49:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v2[i].size(); ++j) ~~^~~~~~~~~~~~~~ main.cpp:65:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v2[0].size(); ++i) ~~^~~~~~~~~~~~~~