Compilare: main.cpp: In function 'int main()': main.cpp:18:10: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[n]=NULL; ^~~~ main.cpp:12:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("paranteze2.in","r",stdin); ^ main.cpp:13:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("paranteze2.out","w",stdout); ^ main.cpp:16:24: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets(s,NMAX,stdin); ^