#include<iostream> #include<vector> using namespace std; int main() { int a,b; vector<bool> v(1000001,1); v[1]=0; //埃拉托色尼筛选算法 for(int i=2; i<=1000000; i++) { if(v[i]) { for(int j=i*2; j<=1000000; j+=i) v[j]=0; } } while(cin>>a>>b) { //[a,b] int count=0; for(int i=a; i<=b; i++) { if(v[i]) count++; } cout<<count<<endl; } } |
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