Compilare: user.cpp: In function ‘int main()’: user.cpp:80:8: warning: unused variable ‘st’ [-Wunused-variable] int st, dr, ones = pref1[r] - pref1[l - 1]; ^~ user.cpp:80:12: warning: unused variable ‘dr’ [-Wunused-variable] int st, dr, ones = pref1[r] - pref1[l - 1]; ^~ user.cpp:51:31: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d\n", &n, &q); ^ user.cpp:52:30: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(str + 1, MAX_N+2, fin); ^ user.cpp:71:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d", &l, &r); ^