Compilare: user.cpp: In function ‘int main()’: user.cpp:67:12: warning: unused variable ‘a’ [-Wunused-variable] int i, a, b, P; ^ user.cpp:67:15: warning: unused variable ‘b’ [-Wunused-variable] int i, a, b, P; ^ user.cpp: In function ‘void read()’: 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:41:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &a, &b, &c); ^ user.cpp: In function ‘int main()’: user.cpp:69:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("party.in", "r", stdin); ^ user.cpp:70:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("party.out", "w", stdout); ^