Compilare: user.cpp: In function ‘int get_num(int&)’: user.cpp:12:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(p<e.size()&&'0'<=e[p]&&e[p]<='9'){ ^ user.cpp: In function ‘int main()’: user.cpp:23:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<e.size(); i++){ ^ user.cpp:24:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i<e.size()&&'0'<=e[i]&&e[i]<='9'){ ^