Compilare: user.cpp: In function ‘int main()’: user.cpp:102:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i <= N; i++) { ^ user.cpp:109:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < M; i++) { ^ user.cpp:115:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i <= freq[0]; i++) { ^ user.cpp:118:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 1; j < M; j++) { ^ user.cpp:120:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < M; i++) { ^ user.cpp:126:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (k = 1; k <= freq[j]; k++) { ^ user.cpp:135:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < M; i++) { ^ user.cpp:101:29: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d %d", &N, &M); ^ user.cpp:103:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%u", &val); ^ user.cpp:143:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("raco.out", "w", stdout); ^