Compilare: user.cpp: In function ‘int main()’: user.cpp:53:13: warning: unused variable ‘j’ [-Wunused-variable] long i, j; ^ user.cpp:55:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("lazy.in", "r", stdin); ^ user.cpp:56:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("lazy.out", "w", stdout); ^ user.cpp:57:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld %ld", &N, &M); ^ user.cpp:64:53: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld %ld %lld %lld", &a, &b, &C1, &C2); ^