lightoj 1007

预先处理好phi数组和前缀和，水题。

#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAXN = 5e6+10;
unsigned long long int phi[MAXN];
void init(){
    for(int i = 1;i < MAXN;i ++) phi[i] = i;
    for(int i = 2;i < MAXN;i += 2) phi[i] /= 2;
    for(int i = 3;i < MAXN;i += 2){
        if(i == phi[i]){
            for(int j = i;j < MAXN;j += i)
                phi[j] = (phi[j]*(i-1)/i);
        }
    }
    for(int i = 1;i < MAXN;i ++) phi[i] = phi[i-1] + phi[i]*phi[i];
}
int main(){
    init();
    int t, a, b, CASE(0);
    scanf("%d", &t);
    while(t--){
        scanf("%d%d", &a, &b);
        printf("Case %d: ", ++CASE);
       printf("%llu
",phi[b]-phi[a-1] );
    }
    return 0;
}