Compilare: main.cpp: In function 'int main()': main.cpp:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int a = 0; a<c.size(); a++) ~^~~~~~~~~ main.cpp:31:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int b = a+1; b<c.size(); b++) ~^~~~~~~~~