Compilare: main.cpp: In function 'int main()': main.cpp:19:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(register int i=1;i<s.size();i++) ~^~~~~~~~~ main.cpp:38:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(register int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:56:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(register int i=1;i<=s.size();i++) ~^~~~~~~~~~ main.cpp:58:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(register int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:11:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.in","r",stdin); ^ main.cpp:12:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.out","w",stdout); ^ main.cpp:14:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&c); ^