Compilare: user.cpp: In function ‘int main()’: user.cpp:6:30: warning: suggest parentheses around assignment used as truth value [-Wparentheses] for(j=(1<<n)-1,i=k-1,x[0]=l=1;i>k-n-1;i--,j-=l,l<<=1) ^ user.cpp:5:109: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biti.in","r",stdin),freopen("biti.out","w",stdout),scanf("%d",&n),printf("%d\n",(k=(1<<n)+n-1)); ^ user.cpp:5:109: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] user.cpp:5:109: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]