Compilare: user.cpp: In function ‘int main()’: user.cpp:50:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < M.size(); i++){ ^ user.cpp:51:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < M[i].size(); j++) ^ user.cpp:41:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d%d", &n, &m); ^ user.cpp:44:34: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d%d", &x, &y); ^