Compilare: main.cpp: In function 'int main()': main.cpp:17:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<s.size();i++) ~^~~~~~~~~ main.cpp:52:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=1;j<s.size()-1;j++) ~^~~~~~~~~~~ main.cpp:67:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(register int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:9:36: 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:10:38: 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:12:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&c); ^