Compilare: user.cpp: In function ‘int main()’: user.cpp:73:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(S1.size() > D) ~~~~~~~~~~^~~ user.cpp:25:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("slidingwindow.in","r",stdin); ^ user.cpp:26:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("slidingwindow.out","w",stdout); ^