Compilare: user.cpp: In function ‘int main(int, char**)’: user.cpp:38:66: 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:51:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (a[i].size()>0 && a[i].find_first_of(":")!=-1) { ^ user.cpp:54:70: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (a[i].substr(0, a[i].find_first_of(",")).find_first_of(34) != -1) { ^