Compilare: user.cpp: In function ‘int main()’: user.cpp:56:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0; j<s.size(); ++j) ^ user.cpp:61:56: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (s[j]<='9' && s[j]>='0' && j<s.size()) x=x*10+s[j++]-'0'; ^ user.cpp:55:13: warning: unused variable ‘x’ [-Wunused-variable] int x=0; ^ user.cpp:81:9: warning: unused variable ‘mx’ [-Wunused-variable] int mx=0; ^