Compilare: user.cpp: In function ‘int main()’: user.cpp:25:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < l[i].size(); j++) ^ user.cpp:37:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k = 0; k < v[j].size(); k++) ^ user.cpp:14:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nrcuv.in", "r", stdin); ^ user.cpp:15:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nrcuv.out", "w", stdout); ^ user.cpp:16:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n", &n, &m); ^ user.cpp:18:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%c %c\n", &x, &y); ^