读入挂

int Scan()

{

    int res = 0, ch, flag = 0;

    if((ch = getchar()) == ‘-‘)             //判断正负

        flag = 1;

    else if(ch >= ‘0‘ && ch <= ‘9‘)           //得到完整的数

        res = ch - ‘0‘;

    while((ch = getchar()) >= ‘0‘ && ch <= ‘9‘ )

        res = res * 10 + ch - ‘0‘;

    return flag ? -res : res;

}  //数字