Submission

Score: 100

User: gay69

Problemset: สามสหาย

Language: cpp

Time: 0.008 second

Submitted On: 2025-08-26 20:47:10

#include <bits/stdc++.h>
using namespace std;
bool isPrime(int n){
    if(n<2){
        return false;
    }
    if(n%2==0){
        return false;
    }
    for(int i=2;i*i<=n;i++){
        if(n%i==0){
            return false;
        }
    }
    return true;
}
int main(){
    int a,b;
    cin >> a>>b;
    int count =0;
    int p[15001]={};
    for(int i=0;i<=15000;i++){
        if(isPrime(i)==true){
            p[i]++;
        }
        p[i] += (i == 0 ? 0 : p[i - 1]);
    }
    for(int i=a;i<=b;i++){
        for(int j=i;j<=b;j++){
            count += p[i + j + b] - p[i + 2 * j - 1];
        }
    }
    cout <<count;
}