The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 5917    Accepted Submission(s): 2498 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 #include<stdio.h> #include<string.h> #define LL long long LL p[3000010]; void get() { memset(p,0,sizeof(p)); for(int i=2;i<3000010;i++) { if(!p[i]) for(int j=i;j<3000010;j+=i) { if(!p[j]) p[j]=j; p[j]=p[j]*(i-1)/i; } } for(int i=3;i<3000010;i++) p[i]+=p[i-1]; } int main() { int a,b; get(); //printf("%lld\n",p[3]); while(~scanf("%d%d",&a,&b)) { printf("%lld\n",p[b]-p[a-1]); } return 0; }