本地过洛谷CE

#include <bits/stdc++.h>
using namespace std;
int pri[10000000]={2,2};
int l,r;
bool isprim(int x)
{
    if(pri[x]!=0) return (pri[x]==1?1:0);
    if(x==2) return 1;
    for(int i=2;i*i<=x;i++)
    {
        if(x%i==0)
        {
            for(int i=1;i*x<r;i++)
            {
                pri[i*x]=2;
            }
            return 0;
        }
    }
    pri[x]=1;
    return 1;
}
int huiwen(long long x){
    long long sum=0,t=x;
    while(t)
    {
        sum=sum*10+t%10;
        t/=10;
    }
    return x==sum;
}
int main()
{
    cin>>l>>r;
    if(l%2==0) l++;
    for(int i=l;i<=r;i+=2)
    {
        if(isprim(i)&&huiwen(i)) cout<<i<<endl;
    }
    return 0;
}