Compilare: user.cpp: In function ‘int main()’: user.cpp:20:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, n, m, op, a, b, ta, tb; ^ user.cpp:21:34: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, 200000, stdin); ^ user.cpp: In function ‘void read(int&)’: user.cpp:14:104: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while(buff[pos] < '0' || buff[pos] > '9')if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0; ^ user.cpp:16:139: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while('0' <= buff[pos] && buff[pos] <= '9') {nr = nr * 10 + buff[pos] - '0';if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;} ^