Compilare: main.cpp: In function 'int main()': main.cpp:64:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<gr[i].size(); j++) ~^~~~~~~~~~~~~ main.cpp:111:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ~^~~~~~~~~