Compilare: user.cpp: In function ‘int main()’: user.cpp:18:9: warning: unused variable ‘r1’ [-Wunused-variable] int r1,c1,r2,c2; ^ user.cpp:18:12: warning: unused variable ‘c1’ [-Wunused-variable] int r1,c1,r2,c2; ^ user.cpp:18:15: warning: unused variable ‘r2’ [-Wunused-variable] int r1,c1,r2,c2; ^ user.cpp:18:18: warning: unused variable ‘c2’ [-Wunused-variable] int r1,c1,r2,c2; ^ user.cpp:10:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&N); ^