Compilare: user.cpp: In function ‘int main()’: user.cpp:45:9: warning: unused variable ‘c’ [-Wunused-variable] int c=0; ^ user.cpp: In function ‘bool pairup(int)’: user.cpp:35:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:38:28: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d %d",&N,&M); ^ user.cpp:42:32: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d %d",&x,&y); ^