Compilare: user.cpp: In function ‘int main()’: user.cpp:57:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("spider.in", "r", stdin); ^ user.cpp:58:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("spider.out", "w", stdout); ^ user.cpp:61:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &N, &M); ^ user.cpp:64:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i][j]); ^ user.cpp:89:21: warning: ‘dsty’ may be used uninitialized in this function [-Wmaybe-uninitialized] y += cy[nxt]; ^ user.cpp:88:21: warning: ‘dstx’ may be used uninitialized in this function [-Wmaybe-uninitialized] x += cx[nxt]; ^