char s[16384] ;
unsigned n = 0;

 //  AC  0.001s with this code.
    for(int c = std::getc(stdin); c != EOF; c = std::getc(stdin))
       s[n++] = c;

// and AC 0.015s with   n = fread(s,1,sizeof(s)-1,stdin);  code.

// I'm wonder that  the std::getc faster than fread!!