Compilare: user.cpp: In function ‘void build()’: user.cpp:26:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp:41:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp:51:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:62:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tractomarm.in", "r", stdin); ^ user.cpp:63:43: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tractomarm.out", "w", stdout); ^ user.cpp:65:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:68:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^ user.cpp:80:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &m); ^ user.cpp:82:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^