Compilare: user.cpp: In function ‘void put_element(const int&, const int&)’: user.cpp:123:9: warning: variable ‘mod’ set but not used [-Wunused-but-set-variable] int mod = pos; ^ user.cpp: In function ‘int main()’: user.cpp:161:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grid.in", "r", stdin); ^ user.cpp:162:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grid.out", "w", stdout); ^ user.cpp:163:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &k); ^ user.cpp:170:49: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &x1, &y1, &x2, &y2); ^