Compilare: user.cpp: In function ‘void read()’: user.cpp:21:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "piata.in", "r", stdin ); ^ user.cpp:22:61: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d%d%d%d%d\n", &n, &pi_x, &pi_y, &pf_x, &pf_y ); ^ user.cpp: In function ‘void write()’: user.cpp:51:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "piata.out", "w", stdout ); ^ user.cpp: In function ‘int solve()’: user.cpp:33:60: warning: ‘x’ may be used uninitialized in this function [-Wmaybe-uninitialized] s -= x, s += vij(i, pi_y), x = vij(i, pf_y), t += s; ^