Compilare: user.cpp: In function ‘void diag(int, int)’: user.cpp:15:12: warning: unused variable ‘k’ [-Wunused-variable] int x, y, k, num = 1, L; ^ user.cpp: In function ‘void read_and_solve()’: user.cpp:52:12: warning: unused variable ‘k’ [-Wunused-variable] int i, j, k; ^ user.cpp:53:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &N, &M, &K); ^ user.cpp:56:44: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &A[i][j]), s.insert(A[i][j]); ^ user.cpp: In function ‘int main()’: user.cpp:82:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("submatrix.in", "rt", stdin); ^ user.cpp:83:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("submatrix.out", "wt", stdout); ^