题意：说一句话，系统进行回复。周期N = 1999，每次遍历一遍字符串（字长不够N，从头循环），找到第N个剔除。找到最后一次剩余的字符。

1.若为‘？’，输出Yes

2.若为‘   ‘，输出No

3.其余情况，输出No comments

样例：

Does the jury of this programming contest use the
algorithm described in this problem to answer my questions?

Yes

At least, will anybody READ my question?

No

This is
UNFAIR!

No comments

#include<iostream>
#include<cstdio>
using namespace std;

char str[30003];
int fun(int m,int k,int i)//以k为周期，m长度，第i次，输出的编号（0,1,2,...,m-1)
{
    if(i==1)
        return (m+k-1)%m;
    else
        return (fun(m-1,k,i-1)+k)%m;
}
int main()
{
    //freopen("in.txt","r",stdin);
    int len=0;
    while(scanf("%c",&str[0])!=EOF)
    {
        if(str[0]>=' ')
        {
            str[++len]=str[0];//printf(" c = %c\n",str[0]);
        }
    }
    int k=fun(len,1999,len) +1;
    //printf("str[%d] =  %c\n",k,str[k]);
    if (str[k]=='?')
        printf("Yes\n");
    else if (str[k]==' ')
        printf("No\n");
    else
        printf("No comments\n");
    return 0;
}