Compilare: user.c: In function ‘main’: user.c:8:24: warning: variable ‘sum’ set but not used [-Wunused-but-set-variable] unsigned long long sum; ^ user.c:7:17: warning: unused variable ‘k’ [-Wunused-variable] int n,i,N,j,k; ^ user.c:7:15: warning: unused variable ‘j’ [-Wunused-variable] int n,i,N,j,k; ^ user.c:9:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ user.c:11:15: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&N); ^