Compilare: main.cpp: In function 'int main()': main.cpp:116:10: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[l]=NULL; ^~~~ main.cpp:110:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("next.in","r",stdin); ^ main.cpp:111:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("next.out","w",stdout); ^ main.cpp:114:30: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets(s,MAX_DIGITS,stdin); ^ main.cpp:117:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%lld",&d); ^