Compilare: user.cpp: In function ‘int hs(std::string, int)’: user.cpp:17:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a.size(); ++i) A=(A*BASE+a[i])%md; ^ user.cpp: In function ‘int main()’: user.cpp:37:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=sz; i<b.size(); ++i) { ^