Compilare: user.cpp: In member function ‘const sp sp::operator+(const sp&) const’: user.cpp:20:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=l2;i<ch.size();i++) ^ user.cpp:22:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=l2;i<other.ch.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:56:9: warning: unused variable ‘m’ [-Wunused-variable] int m,i,j,x; ^ user.cpp:56:15: warning: unused variable ‘x’ [-Wunused-variable] int m,i,j,x; ^ user.cpp:57:15: warning: unused variable ‘ans’ [-Wunused-variable] long long ans=0; ^ user.cpp:54:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.in","r",stdin); ^ user.cpp:55:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.out","w",stdout); ^