# include <stdio.h>
int main()
{
  char myst;

  scanf("%c", &myst);

  while(myst != 's')
  {
    printf("do it again!\n");
    scanf("%c", &myst);
  }

  printf("pass!\n");

  return 0;
}
求助：每次输入非s字符后，do it again!显示两次？请大侠指教……