Compilare: user.cpp: In function ‘int main()’: user.cpp:30:18: warning: unused variable ‘l’ [-Wunused-variable] int i, j, k, l; ^ user.cpp:31:36: 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); ^ user.cpp:32:38: 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); ^ user.cpp:33:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:36:56: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(k=1; k<=i; ++k)scanf("%d", &a[i][j][k]); ^