Compilare: user.cpp: In function ‘int main()’: user.cpp:10:17: warning: variable ‘dr’ set but not used [-Wunused-but-set-variable] int n,a,b,i,dr,s,x; ^~ user.cpp:11:35: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf (fin,"%d%d%d",&n,&a,&b); ^