Compilare: main.cpp: In function 'int main()': main.cpp:25:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s.size()!=n){ ~~~~~~~~^~~ main.cpp:10:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sume.in","r",stdin); ^ main.cpp:11:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sume.out","w",stdout); ^