Submission

PPPPPPPPPP

Score: 100

User: hmmm

Problemset: สามสหาย

Language: cpp

Time: 0.008 second

Submitted On: 2025-03-20 16:11:22

#include<bits/stdc++.h>
using namespace std;
const int N=5005;
bool a[N*3];
vector<int> p;
int mp[N*3];

int main(){
  ios::sync_with_stdio(0); cin.tie(0);
  for(int i=2;i*i<N*3;i++){
    if(a[i]) continue;
    for(int j=i*i;j<N*3;j+=i){
      a[j]=true;
    }
  }
  long long int ans=0;
  int l,r;
  cin >> l >> r;
  int x=l*3,y=r*3;
  for(int i=x;i<=y;i++){
    if(!a[i]) p.push_back(i);
  }
  for(int i=l;i<=r;i++){
    int sum=i*3;
    for(auto e:p){
	  if(sum>e) continue;
      int x=e-sum;
      int mx=min(x,r-i);
      int cnt=2*mx-x+1;
      if(x>mx*2) continue;
      ans+=(cnt+1)/2;
    //   cout << e << ' ' << sum << ' ' << (mx+1)/2 << "\n";
    }
  }
  cout << ans;
}