Compilare: main.cpp: In function 'long long unsigned int check(long long unsigned int)': main.cpp:9:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=n;i++) ~^~~ main.cpp: In function 'int main()': main.cpp:21:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=n;i++) ~^~~