Compilare: main.cpp: In function 'int main()': main.cpp:21:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<a.size(); i++){ ~^~~~~~~~~ main.cpp:32:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<b.size(); i++){ ~^~~~~~~~~ main.cpp:36:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<c.size(); i++){ ~^~~~~~~~~ main.cpp:42:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<sol.size(); i++){ ~^~~~~~~~~~~