Compilare: user.cpp: In function ‘int main()’: user.cpp:58:17: warning: unused variable ‘xx’ [-Wunused-variable] int xx=lin.front(); ^ user.cpp:59:17: warning: unused variable ‘yy’ [-Wunused-variable] int yy=col.front(); ^ user.cpp:36:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("taxa.in", "r",stdin); ^ user.cpp:37:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("taxa.out", "w",stdout); ^ user.cpp:40:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:41:42: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d", &sl, &sc, &fl, &fc); ^ user.cpp:44:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &mat[i][j]); ^