Compilare: main.cpp: In function 'int main()': main.cpp:104:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int a = 0; a < f.size(); a++) ~~^~~~~~~~~~ main.cpp:112:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int a = 0; a < c.size(); a++) ~~^~~~~~~~~~