Compilare: user.cpp: In function ‘int main()’: user.cpp:55:30: warning: operation on ‘y2’ may be undefined [-Wsequence-point] x1=y2=x2=y2=0; ^ user.cpp:23:31: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%lld%lld",&p,&q); ^ user.cpp:33:39: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%lld%lld",&a,&b); ^