OJ-Problems-Source/HDOJ/2197_autoAC.cpp

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#include<stdio.h>
#include<iostream>
#include<string.h>
#include<math.h>
#include<map>
using namespace std;
map<int,int>mp;
const int MOD=2008;
int fun(int a,int n){
if(n==1)return a;
int num=fun(a,n/2);
num=num*num%MOD;
if(n%2==1)num=num*a%MOD;
return (num+MOD)%MOD;
}
int cal(int n){
if(mp[n]!=0)return mp[n];
mp[n]=fun(2,n)-2;
for(int i=2;i*i<=n;i++){
if(n%i==0){
mp[n]=(mp[n]-cal(i)+MOD)%MOD;
if(i*i!=n)mp[n]=(mp[n]-cal(n/i)+MOD)%MOD;
}
}
return mp[n];
}
int main()
{
int n;
while(scanf("%d",&n)!=EOF){
mp[0]=0;
mp[1]=2;
mp[2]=2;
if(n<=2){cout<<mp[n]<<endl;continue;}
int ans=cal(n);
cout<<ans<<endl;
}
return 0;
}