Compilare: user.cpp: In function ‘int main()’: user.cpp:84:15: warning: unused variable ‘x’ [-Wunused-variable] int i, j, x, y, num, v, w, ans = 0, yy, xx; ^ user.cpp:84:18: warning: unused variable ‘y’ [-Wunused-variable] int i, j, x, y, num, v, w, ans = 0, yy, xx; ^ user.cpp:84:21: warning: unused variable ‘num’ [-Wunused-variable] int i, j, x, y, num, v, w, ans = 0, yy, xx; ^ user.cpp:84:26: warning: unused variable ‘v’ [-Wunused-variable] int i, j, x, y, num, v, w, ans = 0, yy, xx; ^ user.cpp:84:29: warning: unused variable ‘w’ [-Wunused-variable] int i, j, x, y, num, v, w, ans = 0, yy, xx; ^ user.cpp:86:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("submatrix.in", "r", stdin); ^ user.cpp:87:43: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("submatrix.out", "w", stdout); ^ user.cpp:89:33: 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:92:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &a [i][j]); ^