Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

var scanner = bufio.NewScanner(os.Stdin)

const (
	MAX  = 1000000
	SQRT = 1000
)

func main() {
	comp := make([]int, MAX+2)
	sieve := func() {
		for i := 3; i < SQRT; i += 2 {
			if comp[i] == 0 {
				for j := i * i; j < MAX; j += i {
					comp[j] = 1
				}
			}
		}
	}
	sieve()
	tbl := make([]int, MAX+2)
	tbl[2] = 1
	k := 1
	for i := 3; i < MAX; i += 2 {
		if comp[i] == 0 {
			k++
		}
		tbl[i+1], tbl[i] = k, k
	}
	for scanner.Scan() {
		n, _ := strconv.Atoi(scanner.Text())
		if n == 0 {
			break
		}
		ans := 0
		for i := 0; i < n; i++ {
			scanner.Scan()
			buf := strings.Split(scanner.Text(), " ")
			p, _ := strconv.Atoi(buf[0])
			m, _ := strconv.Atoi(buf[1])
			a, b := p-m, p+m
			if a < 2 {
				a = 2
			}
			if b > MAX {
				b = MAX
			}
			ans += tbl[b] - tbl[a-1] - 1
		}
		if ans < 0 {
			ans = 0
		}
		fmt.Println(ans)
	}
}

C++: #include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;


#define MAX_N 1000000
int prime[MAX_N];//i番目の素数
bool is_prime[MAX_N+1];
int sieve(int n){
	int p=0;
	memset(is_prime,true,sizeof(is_prime));
	is_prime[0]=is_prime[1]=false;
	for(int i=2;i<=n;i++){
		if(is_prime[i]){
			prime[p++]=i;
			for(int j=2*i;j<=n;j+=i)is_prime[j]=false;
		}
	}
	return p;
}


int main(){
	int num=sieve(MAX_N),n;
	while(cin>>n&&n){
		int ans=0,x;
		int p,m;
		for(int i=0;i<n;i++){
			cin>>p>>m;
			x=upper_bound(prime,prime+num,p+m)-lower_bound(prime,prime+num,p-m);
			if(x==0)ans--;
			else ans+=x-1;
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: //include
//------------------------------------------
#include <bits/stdc++.h> // only for GCC

using namespace std;

//typedef
//------------------------------------------
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;

//container util
//------------------------------------------
#define all(a)  (a).begin(),(a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define pb push_back
#define mp make_pair

//repetition
//------------------------------------------
#define loop(i,a,b) for(ull i=(a);i<ull(b);++i)
#define rep(i,n) loop(i,0,n)
#define iter(i,c) for(auto i=(c).begin(); i!=(c).end(); ++i)
#define riter(i,c) for(auto i=(c).rbegin(); i!=(c).rend(); ++i)

//constant
//--------------------------------------------
const double eps = 1e-10;
const double pi  = acos(-1.0);
const double inf = (int)1e8;

// output vector
// ------------------------------------------
namespace std {
    template<typename T>ostream&operator<<(ostream&os, vector<T>const&v){
        iter(it,v) os<<*it<<(it+1==v.end()?"":",");
        return os;
    }
    template<typename T, typename U>ostream&operator<<(ostream&os,const pair<T,U>&p){
        return os << "[" << p.dirst << "," << p.second << "]";
    }
}

//clear memory
// ------------------------------------------
#define clr(a,i) memset((a), (i) ,sizeof(a))

int lcm(int a,int b){
   return a*b/__gcd(a,b);
}
 
vb pn(999984); 
void prime_number(ull n){
   fill(all(pn),1);
   pn[0]=false;pn[1]=false;
   loop(i,2,n/2+1){
      if(!pn[i]) continue;
      for(ull j=2;i*j<=n;j++){
         pn[i*j]=false;
      }
   }
}

int main(){
   ull n,s,g;
   ll p,m;
   int x;
   prime_number(999983);
   while(cin >> n&&n){
      x=0;
      rep(i,n){
         cin>>p>>m;
         if(p-m<2) s=2;
         else s=p-m;
         if(p+m>999983) g=999984;
         else g=p+m+1;
         x+=(count(pn.begin()+s,pn.begin()+g,1)-1);
      }
      cout << x << endl;
   }
   return 0;
}

C++: #include <algorithm>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <string>
#include <queue>
#define MAX 1000001
using namespace std;

int main(void){
	int i,j,k,n,m,p,x,sum;
	bool a[MAX];

	for(i=0;i<MAX;i++) a[i] = true;
	for(i=2;i<MAX;i++){
		if(a[i]){
			for(j=i+i;j<MAX;j+=i) a[j] = false;
		}
	}

	while(1){
		cin >> n;
		if(n == 0) break;
		sum = 0;
		for(i=0;i<n;i++){
			x = 0;
			cin >> p >> m;
			for(j=p-m;j<=p+m;j++){
				if(j < 2) continue;
				if(j >= MAX) break;
				if(a[j]) x++;
			}
			//if(x == 0) x = 1;
			sum += x - 1;
		}
		cout << sum << endl;
	}
	return 0;
}

C++: #include<iostream>
#include <algorithm>
#include<functional>//greaterの使用
using namespace std;
#define MAX_LIST 999983+100
#define MP 999983

int main(){
	bool prime[MAX_LIST];
	for(int i=0;i<MAX_LIST;i++){
		prime[i]=1;
	}
	prime[0]=prime[1]=0;
	for(int i=0;i*i<MAX_LIST;i++){
		if(prime[i]==1){
			for(int j=i*2;j<MAX_LIST;j=j+i){
				prime[j]=0;
			}
		}
	}
	for(int i=MP+1;i<MAX_LIST;i++){
		prime[i]=0;
	}
	
	int prime_num[MAX_LIST];
	prime_num[0]=1;
	for(int i=1;i<MP;i++){
		prime_num[i]=prime_num[i-1]+prime[i];
	}
	
	
	int pair_num;
	while(cin>>pair_num,pair_num){
		int ans=0;
		
		for(;pair_num--;){
			int p,m;
			int x;
			cin>>p;
			cin>>m;
			
			if(p+m>MP){
				x=prime_num[MP]-prime_num[p-m];
			}else{
				x=prime_num[p+m]-prime_num[p-m];
			}
			ans--;
			/*
			if(x<0){
				ans--;
			}else{
				x--;
				ans=ans+x;
			}*/
		}
		cout<<ans<<endl;
	}
	return 0;
}

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

#define pb(n) push_back(n)
#define fi first
#define se second
#define all(r) (r).begin(),(r).end()
#define gsort(st,en) sort((st),(en),greater<int>())
#define vmax(ary) *max_element(all(ary))
#define vmin(ary) *min_element(all(ary))
#define debug(x) cout<<#x<<": "<<x<<endl
#define fcout(n) cout<<fixed<<setprecision((n))
#define scout(n) cout<<setw(n)
#define vary(type,name,size,init) vector< type> name(size,init)

#define rep(i,n) for(int i = 0; i < (int)(n);++i)
#define REP(i,a,b) for(int i = (a);i < (int)(b);++i)
#define repi(it,array) for(auto it = array.begin(),end = array.end(); it != end;++it)
#define repa(n,array) for(auto &n :(array))

using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using dict = map<string,int>;
using pii = pair<int,int> ;

constexpr int imax = ((1<<30)-1)*2+1 ;
constexpr int inf = 100000000;
constexpr double PI = acos(-1.0) ;
double eps = 1e-10 ;
const int dy[] = {-1,0,1,0};
const int dx[] = {0,-1,0,1};

inline bool value(int x,int y,int w,int h){
  return (x >= 0 && x < w && y >= 0 && y < h);
}

template<typename T>
void Unique(vector<T> &v){
  sort(all(v));
  v.erase(unique(all(v)),v.end());
}

template<typename T>
T ston(string& str, T n){
  istringstream sin(str) ;
  T num ;
  sin >> num ;
  return num ;
}

void Ans(bool f){
  if(f) cout << "YES"<<endl;
  else cout << "NO"<<endl;
}

const int PrimeMax = 1000001;
int is_prime[1000001],sum[1000001*2];
void Eratosthenes(int N){
  for(int i = 0; i < N; i++){
    is_prime[i] = 1;
  }
  is_prime[0] = 0;
  is_prime[1] = 0;
  for(int i = 2; i < N ; i++){
    if(is_prime[i]){
      for(int j = i*2; j < N; j+=i){
        is_prime[j] = 0;
      }
    }
  }
  REP(i,0,N){
    sum[i+1] = sum[i] + is_prime[i];
  }
  REP(i,N,2*N){
    sum[i+1] = sum[i];
  }
}
int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  Eratosthenes(PrimeMax);
  while(cin>>n && n){
    ll p,m,ans = 0;
    rep(i,n){
      ll f,s;
      cin >> p>>m;
      s = max(0LL,p-m-1);
      f = p+m;
      ans += (sum[f]-sum[s])-1;
    }
    cout << ans << endl;
  }
  return 0;
}