显然的区间筛法

#include
    
      #include
     
      #include
      
       #include
       
        using namespace std;typedef long long ll;ll L,R,k,n;const int MAXN = 10000005;int prime[MAXN],tot;bool isx[MAXN];void mkprime(){    for(int i=2;i<=n;i++){        if(!isx[i]){prime[++tot]=i;}        for(int j=1;i*prime[j]<=n&&j<=tot;j++){            int v=prime[j];            isx[i*v]=1;            if(i%v==0)break;            }    }}bool vis[MAXN];int main(){    freopen("prime.in","r",stdin);    freopen("prime.out","w",stdout);    cin>>L>>R>>k;    n=sqrt(R);    n=min(n,k);    mkprime();    for(int i=1;i<=tot;i++){        int v=prime[i];        ll cur=1ll*v*(L/v);        if(cur