Compilare: user.cpp: In function ‘int cnt(const string&, const string&)’: user.cpp:21:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < b.size(); ++i) { ^ user.cpp:28:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < a.size(); ++i) { ^ user.cpp:30:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 1; j < b.size(); ++j) { ^ user.cpp: In function ‘int solve(const string&)’: user.cpp:50:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ^