HOU 2824 The Euler function 欧拉函数

The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3817    Accepted Submission(s): 1580

Problem Description

The Euler function phi is an important kind of function in number theory, (n) represents the amount of the numbers which are smaller than n and coprime to n, and this function has a lot of beautiful characteristics. Here comes a very easy question: suppose you are given a, b, try to calculate (a)+ (a+1)+....+ (b)

 

Input

There are several test cases. Each line has two integers a, b (2<a<b<3000000).

 

Output

Output the result of (a)+ (a+1)+....+ (b)

 

Sample Input

3 100

 

Sample Output

3042

/*HODJ 2824 欧拉函数 欧拉函数的定义:E(k)=([1,n-1]中与n互质的整数个数).(a为N的质因数) 若(N%a==0 && (N/a)%a==0) 则有:E(N)=E(N/a)*a; 若(N%a==0 && (N/a)%a!=0) 则有:E(N)=E(N/a)*(a-1);*/#include<iostream>#include<stdio.h>#include<algorithm>using namespace std;#define N 3000001int phi[N];void phi_table(){int i,j;memset(phi,0,sizeof(phi));phi[1]=1;for(i=2;i<=N;i++){if(!phi[i]){for(j=i;j<=N;j+=i){if(!phi[j])phi[j]=j;phi[j]=phi[j]/i*(i-1);}}}}int main(){int i,a,b;__int64 ans;phi_table();//freopen("test.txt","r",stdin);while(scanf("%d%d",&a,&b)!=EOF){ans=0;for(i=a;i<=b;i++)ans+=(__int64)phi[i];printf("%I64d\n",ans);}return 0;}