Compilare: user.cpp: In member function ‘void nrmare::ch(std::vector<int>&, std::vector<int>&)’: user.cpp:29:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; a.size() < L; a.push_back(0)); ^ user.cpp:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; b.size() < L; b.push_back(0)); ^ In file included from /usr/include/c++/4.8/cassert:43:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:33, from user.cpp:1: user.cpp:31:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] assert(a.size() == L); ^ user.cpp:32:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] assert(b.size() == L); ^ user.cpp: In function ‘int main()’: user.cpp:63:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sg1.out", "w", stdout); ^