Compilare: user.cpp: In function ‘int main()’: user.cpp:20:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < l[0].size(); i++) ^ user.cpp:25:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < l[i].size() - 1; j++) ^ user.cpp:26:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k = j + 1; k < l[i].size(); k++) ^ user.cpp:12:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("divk.in", "r", stdin); ^ user.cpp:13:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("divk.out", "w", stdout); ^ user.cpp:14:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d", &n, &K, &a, &b); ^ user.cpp:16:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^