Compilare: user.cpp: In function ‘int main()’: user.cpp:63:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v[i].size(); ++j) ^ user.cpp:42:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ndap.in", "r", stdin); ^ user.cpp:43:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ndap.out", "w", stdout); ^ user.cpp:47:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:49:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &a, &b); ^