View Code of Problem 103

#include<bits/stdc++.h>
using namespace std;

int main(void)
{
  int sum,i,j,a,b;
  vector <int> su(1000001,1);
  su[0],su[1]=0,0;
  for(i=2;i<1000000;++i)
  {
    if(su[i]==1)
    {
      for(j=2*i;j<=1000000;j+=i)
        su[j]=0;
    }
  }
  vector <int> dp(1000001,0);
  dp[0],dp[1]=0,0;
  for(i=2;i<=1000000;++i)
    dp[i]=dp[i-1]+su[i];
  while(cin>>a>>b)
  { 
    cout<<dp[b]-dp[a-1]<<endl;
  }
}