#include <bits/stdc++.h> using namespace std; long int issushu(long int n ) { if(n==1||n==2) return 1; else { for(int i=2;i<=sqrt(n);i++) if(n%i==0) return 0; } return 1; } int main() { long int n,i,a,b; bool hashtable[1000010]={false}; for(i=0;i<1000010;i++) { if(issushu(i)) hashtable[i]=true; } while(cin>>a>>b) { long int k=0; for(i=a;i<=b;i++) { if(hashtable[i]==true) k++; } cout<<k<<endl; } } |
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