Submission

Score: 100

User: qweqwe

Problemset: สามสหาย

Language: cpp

Time: 0.038 second

Submitted On: 2026-10-09 09:21:16

/*
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*/
#include <bits/stdc++.h>
#define akneru cin.tie(0)->sync_with_stdio(0)
using namespace std;
using ll = long long;
using pii = pair<ll,ll>;
using vi = vector<ll>;
using vvi = vector<vector<ll>>;
using db = long double;

int main(){
	akneru;
	int a,b;cin >> a >> b;
	vi primes;
	for (int i=2;i<=16000;i++){
		bool yes=1;
		for (int j=2;j*j<=i;j++){
			if (i%j==0){
				yes=0;break;
			}
		}if (yes)primes.push_back(i);
	}
	ll cnt=0;
	for (int i=a;i<=b;i++){
		int pos1=0,pos2=0;
		for (int j=i;j<=b;j++){
			int r=i+j;
			while (primes[pos1]<max(r+a,r+j)) pos1++;
			while (primes[pos2] <= max(r+b,r+j)) pos2++;
			pos2--;
			//cout << i << " " << j << " " << primes[pos1] << " " << primes[pos2] << "\n";
			if (pos1 > pos2) continue;
			cnt += pos2-pos1+1;
		}
	}cout << cnt;
	return 0;
}