Compilare: main.cpp: In function 'int main()': main.cpp:22:18: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] s[i+1]=NULL; ^~~~ main.cpp:5:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("numar3.in","r",stdin); ^ main.cpp:6:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("numar3.out","w",stdout); ^ main.cpp:10:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&k); ^ main.cpp:11:27: warning: ignoring return value of 'char* fgets(char*, int, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fgets(s,5000000,stdin); ^