The Euler function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 6449    Accepted Submission(s): 2720 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<cstdio> #include<cstring> const int maxn = 3000010; long long phi[maxn]; void Euler(){ for(int i = 2; i < maxn ; i++){ if(!phi[i]){ for(int j = i; j < maxn; j += i){ if(!phi[j]) phi[j] = j; phi[j] = phi[j] / i * (i-1); } } } for(int i = 3; i < maxn; i++) phi[i] += phi[i-1]; } int main(){ int a,b; Euler(); while(~scanf("%d%d",&a,&b)){ printf("%lld\n",phi[b] - phi[a-1]); } return 0; }