Compilare: main.cpp: In function 'int main()': main.cpp:20:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("drum2.in", "r", stdin); ^ main.cpp:21:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("drum2.out", "w", stdout); ^ main.cpp:23:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ main.cpp:24:80: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] for (int i = 1; i <= n * (n + 1) * (2 * n + 1) / 6; i++) scanf("%d", &a[i]); ^