TOJ 4118 IQ test

It's a simple problem;

The portal:http://acm.tju.edu.cn/toj/showp4118.html

#include <cstdio>#include <cstdlib>#include <cmath>#include <cstring>int f[3000005];int num[1000005];void Pre_deal(){    memset(f,0,sizeof(f));    memset(num,0,sizeof(num));    for(int i=1;i<=1000000;i++){        if(!f[i])f[2*i+2] = 1;    }    for(int i=1;i<=1000000;i++){        num[i] = num[i-1] + 1  - f[i];    }}void Deal_with(){    int n;    while(~scanf("%d",&n)){        printf("%d\n",num[n]);    }}int main(void){    Pre_deal();    Deal_with();    return 0;}