#include<iostream>#include<vector>using namespace std;vector<bool>arr(1000001,true);void calculation();int sum(int a);void calculation(){ arr[0]=arr[1]=false; for(int i=2;i*i<=1000000;i++){ if (!arr[i]) continue; for(int j=i*i;j<=1000000;j+=i) arr[j]=false; } }int sum(int a){...