Compilare: user.cpp: In function ‘int main(int, char**)’: user.cpp:38:68: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (expression.size() > 0 && expression.find_first_of(",") != -1) { ^ user.cpp:49:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size() - 1; i++) { ^ user.cpp:88:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (b[1].find_first_of(34) != -1) { ^ user.cpp:112:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i != a.size() - 2) { ^