Compilare: user.cpp: In function ‘int main()’: user.cpp:58:53: warning: operation on ‘k’ may be undefined [-Wsequence-point] v[++k]=(v[k-2] * i + v[k-1]* j + 1) % 10; ^ user.cpp:58:53: warning: operation on ‘k’ may be undefined [-Wsequence-point] user.cpp:45:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("qmatrix.in", "r", stdin); ^ user.cpp:46:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("qmatrix.out", "w", stdout); ^ user.cpp:48:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &n, &x, &y, &q); ^ user.cpp:66:42: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("\n%c %d %d", &lit, &c, &p); ^