Compilare: user.cpp: In function ‘int main()’: user.cpp:15:12: warning: unused variable ‘a’ [-Wunused-variable] int n, a, b; ^ user.cpp:15:15: warning: unused variable ‘b’ [-Wunused-variable] int n, a, b; ^ user.cpp:29:9: warning: unused variable ‘k’ [-Wunused-variable] int k = u[0]; ^ user.cpp:16:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d", &n); ^ user.cpp:18:42: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d", &x[i], &y[i]); ^