Compilare: user.cpp: In function ‘int main()’: user.cpp:77:9: warning: unused variable ‘st’ [-Wunused-variable] int st = 0, dr = N * M, mid, ans = -1; ^ user.cpp:77:17: warning: unused variable ‘dr’ [-Wunused-variable] int st = 0, dr = N * M, mid, ans = -1; ^ user.cpp:77:29: warning: unused variable ‘mid’ [-Wunused-variable] int st = 0, dr = N * M, mid, ans = -1; ^ user.cpp:72:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(in, "r", stdin); ^ user.cpp:73:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(out, "w", stdout); ^ user.cpp:74:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n", &N, &M); ^ user.cpp: In function ‘void Init()’: user.cpp:102:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%c", &ch); ^ user.cpp:100:5: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(register int i = 1; i <= N; ++ i, scanf("%c", &ch)) ^