Compilare: user.cpp: In function ‘int main()’: user.cpp:14:14: warning: statement has no effect [-Wunused-value] for(a;a<p;a++) ^ user.cpp:8:33: warning: unused variable ‘S’ [-Wunused-variable] unsigned long long a=1,L1,i,S=0,ok,L,n,p,x; ^ user.cpp:36:9: warning: ‘ok’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(ok==0) ^