Compilare: main.cpp: In function 'void precalc()': main.cpp:15:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < a.size(); ++i){ ~~^~~~~~~~~~ main.cpp: In function 'void postcalc()': main.cpp:30:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < b.size(); ++j){ ~~^~~~~~~~~~ main.cpp:37:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == a.size()){ ~~^~~~~~~~~~~