Compilare: user.cpp:3:21: warning: integer overflow in expression [-Woverflow] long long mx=-(1<<31); ^ user.cpp: In function ‘void back(int)’: user.cpp:24:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(valid(k)) ^ user.cpp: In function ‘int main()’: user.cpp:44:20: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘long long int’ [-Wformat=] printf("%d", mx); ^ user.cpp:36:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("flip.in","r",stdin); ^ user.cpp:37:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("flip.out","w",stdout); ^ user.cpp:39:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:42:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &v[i][j]); ^