Compilare: user.cpp: In function ‘void read()’: user.cpp:31:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) a[i] = i; ^ user.cpp:33:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < x.size(); i++) ^ user.cpp: In function ‘void solve()’: user.cpp:44:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) ^ user.cpp: In function ‘void write()’: user.cpp:56:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); i++) ^