#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("inline")
#include<bits/stdc++.h>
using namespace std;
template<class T> struct cLtraits_identity{
  using type = T;
}
;
template<class T> using cLtraits_try_make_signed =
  typename conditional<
    is_integral<T>::value,
    make_signed<T>,
    cLtraits_identity<T>
    >::type;
template <class S, class T> struct cLtraits_common_type{
  using tS = typename cLtraits_try_make_signed<S>::type;
  using tT = typename cLtraits_try_make_signed<T>::type;
  using type = typename common_type<tS,tT>::type;
}
;
void*wmem;
char memarr[96000000];
template<class S, class T> inline auto min_L(S a, T b)
-> typename cLtraits_common_type<S,T>::type{
  return (typename cLtraits_common_type<S,T>::type) a <= (typename cLtraits_common_type<S,T>::type) b ? a : b;
}
template<class S, class T> inline auto max_L(S a, T b)
-> typename cLtraits_common_type<S,T>::type{
  return (typename cLtraits_common_type<S,T>::type) a >= (typename cLtraits_common_type<S,T>::type) b ? a : b;
}
template<class T> inline void walloc1d(T **arr, int x, void **mem = &wmem){
  static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] );
  (*arr)=(T*)(*mem);
  (*mem)=((*arr)+x);
}
template<class T> inline void walloc1d(T **arr, int x1, int x2, void **mem = &wmem){
  walloc1d(arr, x2-x1, mem);
  (*arr) -= x1;
}
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned x){
  int s=0;
  char f[10];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(long long x){
  int s=0;
  int m=0;
  char f[20];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(unsigned long long x){
  int s=0;
  char f[21];
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
int WRITER_DOUBLE_DIGIT = 15;
inline int writerDigit_double(){
  return WRITER_DOUBLE_DIGIT;
}
inline void writerDigit_double(int d){
  WRITER_DOUBLE_DIGIT = d;
}
inline void wt_L(double x){
  const int d = WRITER_DOUBLE_DIGIT;
  int k;
  int r;
  double v;
  if(x!=x || (x==x+1 && x==2*x)){
    my_putchar_unlocked('E');
    my_putchar_unlocked('r');
    my_putchar_unlocked('r');
    return;
  }
  if(x < 0){
    my_putchar_unlocked('-');
    x = -x;
  }
  x += 0.5 * pow(0.1, d);
  r = 0;
  v = 1;
  while(x >= 10*v){
    v *= 10;
    r++;
  }
  while(r >= 0){
    r--;
    k = floor(x / v);
    if(k >= 10){
      k = 9;
    }
    if(k <= -1){
      k = 0;
    }
    x -= k * v;
    v *= 0.1;
    my_putchar_unlocked(k + '0');
  }
  if(d > 0){
    my_putchar_unlocked('.');
    v = 1;
    for(r=(0);r<(d);r++){
      v *= 0.1;
      k = floor(x / v);
      if(k >= 10){
        k = 9;
      }
      if(k <= -1){
        k = 0;
      }
      x -= k * v;
      my_putchar_unlocked(k + '0');
    }
  }
}
inline void wt_L(const char c[]){
  int i=0;
  for(i=0;c[i]!='\0';i++){
    my_putchar_unlocked(c[i]);
  }
}
inline void wt_L(string &x){
  int i=0;
  for(i=0;x[i]!='\0';i++){
    my_putchar_unlocked(x[i]);
  }
}
template<class T> inline T pow2_L(T a){
  return a*a;
}
inline long long Isqrt_f_L(const long long n){
  long long r = sqrt(n);
  r =max_L(r-2, 0);
  while((pow2_L((r+1)))<= n ){
    r++;
  }
  return r;
}
long long cReader_ll(long long mn, long long mx, char nx){
  int i;
  int fg = 0;
  int m = 1;
  int f = -1;
  long long res = 0;
  double tmp = 0;
  for(;;){
    i = my_getchar_unlocked();
    if(fg==0 && i=='-'){
      fg++;
      m = -1;
    }
    else if('0' <= i  &&  i <= '9'){
      fg++;
      if(f == -1){
        f = i - '0';
      }
      res = 10 * res + i - '0';
      tmp = 10 * tmp + i - '0';
      assert(tmp < 1e20);
    }
    else{
      break;
    }
  }
  assert(tmp / 2 <= res);
  assert((m==1 && fg >= 1) || (m==-1 && fg >= 2));
  assert(mn <= m * res  &&  m * res <= mx);
  assert(!(res == 0 && m == -1));
  assert(!(res != 0 && f == 0));
  assert(!(res == 0 && fg >= 2));
  assert(i == nx);
  return m * res;
}
void cReader_eof(){
  int i;
  i = my_getchar_unlocked();
  assert(i == EOF);
}
long long cntPrime(long long n, void *mem = wmem){
  int i;
  int j;
  int k;
  int m;
  int sn;
  int ssn;
  int c;
  char*isp;
  long long*s1;
  long long*s2;
  long long x;
  long long tmp;
  const double nn = n;
  if(n <= 1){
    return 0;
  }
  if(n == 2){
    return 1;
  }
  c = 0;
  sn =Isqrt_f_L(n);
  ssn =Isqrt_f_L(sn);
  walloc1d(&s1, sn+1, &mem);
  walloc1d(&s2, sn+1, &mem);
  walloc1d(&isp, sn+1, &mem);
  s1[0] = 0;
  for(i=(1);i<(sn+1);i++){
    s1[i] = i - 1;
  }
  for(i=(1);i<(sn+1);i++){
    s2[i] = n/i - 1;
  }
  for(i=(2);i<(sn+1);i++){
    isp[i] = 1;
  }
  for(i=(2);i<(ssn+1);i++){
    if(isp[i]){
      for(j=i*i;j<=sn;j+=i){
        isp[j] = 0;
      }
      for(j=(1);j<(sn+1);j++){
        x = (long long) i * j;
        if(x > sn){
          s2[j] -= s1[(int)(nn / x)] - c;
        }
        else{
          s2[j] -= s2[x] - c;
        }
      }
      for(k = (sn+1)/i; k >= i; k--){
        m =min_L(sn+1, i*(k+1));
        tmp = s1[k] - c;
        for(j=(i*k);j<(m);j++){
          s1[j] -= tmp;
        }
      }
      c++;
    }
  }
  for(i=(ssn+1);i<(sn+1);i++){
    if(isp[i]){
      for(j=(1);j<(sn+1);j++){
        x = (long long) i * j;
        if(x * i > n){
          break;
        }
        if(x > sn){
          s2[j] -= s1[(int)(nn / x)] - c;
        }
        else{
          s2[j] -= s2[x] - c;
        }
      }
      c++;
    }
  }
  return s2[1];
}
template<class T> T sumPrime(long long n, void *mem = wmem){
  int i;
  int j;
  int k;
  int m;
  int sn;
  int ssn;
  char*isp;
  long long x;
  T*s1;
  T*s2;
  T c;
  T tmp;
  const double nn = n;
  if(n <= 1){
    return 0;
  }
  if(n == 2){
    return 1;
  }
  c = 0;
  sn =Isqrt_f_L(n);
  ssn =Isqrt_f_L(sn);
  walloc1d(&s1, sn+1, &mem);
  walloc1d(&s2, sn+1, &mem);
  walloc1d(&isp, sn+1, &mem);
  s1[0] = 0;
  for(i=(1);i<(sn+1);i++){
    s1[i] = ((T)i) * ((T)(i+1)) / 2 - 1;
  }
  for(i=(1);i<(sn+1);i++){
    s2[i] = ((T)(n/i)) * ((T)(n/i+1)) / 2 - 1;
  }
  for(i=(2);i<(sn+1);i++){
    isp[i] = 1;
  }
  for(i=(2);i<(ssn+1);i++){
    if(isp[i]){
      for(j=i*i;j<=sn;j+=i){
        isp[j] = 0;
      }
      for(j=(1);j<(sn+1);j++){
        x = (long long) i * j;
        if(x > sn){
          s2[j] -= i * (s1[(int)(nn / x)] - c);
        }
        else{
          s2[j] -= i * (s2[x] - c);
        }
      }
      for(k = (sn+1)/i; k >= i; k--){
        m =min_L(sn+1, i*(k+1));
        tmp = i * (s1[k] - c);
        for(j=(i*k);j<(m);j++){
          s1[j] -= tmp;
        }
      }
      c += i;
    }
  }
  for(i=(ssn+1);i<(sn+1);i++){
    if(isp[i]){
      for(j=(1);j<(sn+1);j++){
        x = (long long) i * j;
        if(x * i > n){
          break;
        }
        if(x > sn){
          s2[j] -= i * (s1[(int)(nn / x)] - c);
        }
        else{
          s2[j] -= i * (s2[x] - c);
        }
      }
      c += i;
    }
  }
  return s2[1];
}
int main(){
  wmem = memarr;
  long long L;
  long long R;
  L = cReader_ll(1, 10000000000LL, ' ');
  R = cReader_ll(L, 10000000000LL, '\n');
  cReader_eof();
  wt_L(cntPrime(2*R) - cntPrime(2*L) + cntPrime(R) - cntPrime(L-1));
  wt_L('\n');
  return 0;
}
// cLay version 20210819-1 [beta]

// --- original code ---
// ll cntPrime(ll n, void *mem = wmem){
//   int i, j, k, m, sn, ssn, c;
//   char *isp;
//   ll *s1, *s2, x, tmp;
//   const double nn = n;
//   if(n <= 1) return 0;
//   if(n == 2) return 1;
// 
//   c = 0;
//   sn = Isqrt_f(n);
//   ssn = Isqrt_f(sn);
//   walloc1d(&s1, sn+1, &mem);
//   walloc1d(&s2, sn+1, &mem);
//   walloc1d(&isp, sn+1, &mem);
// 
//   s1[0] = 0;
//   rep(i,1,sn+1) s1[i] = i - 1;
//   rep(i,1,sn+1) s2[i] = n/i - 1;
//   rep(i,2,sn+1) isp[i] = 1;
// 
//   rep(i,2,ssn+1) if(isp[i]){
//     for(j=i*i;j<=sn;j+=i) isp[j] = 0;
//     rep(j,1,sn+1){
//       x = (ll) i * j;
//       if(x > sn) s2[j] -= s1[(int)(nn / x)] - c;
//       else       s2[j] -= s2[x] - c;
//     }
//     for(k = (sn+1)/i; k >= i; k--){
//       m = min(sn+1, i*(k+1));
//       tmp = s1[k] - c;
//       rep(j,i*k,m) s1[j] -= tmp;
//     }
//     c++;
//   }
// 
//   rep(i,ssn+1,sn+1) if(isp[i]){
//     rep(j,1,sn+1){
//       x = (ll) i * j;
//       if(x * i > n) break;
//       if(x > sn) s2[j] -= s1[(int)(nn / x)] - c;
//       else       s2[j] -= s2[x] - c;
//     }
//     c++;
//   }
// 
//   return s2[1];
// }
// 
// template<class T>
// T sumPrime(ll n, void *mem = wmem){
//   int i, j, k, m, sn, ssn;
//   char *isp;
//   ll x;
//   T *s1, *s2, c, tmp;
//   const double nn = n;
//   if(n <= 1) return 0;
//   if(n == 2) return 1;
// 
//   c = 0;
//   sn = Isqrt_f(n);
//   ssn = Isqrt_f(sn);
//   walloc1d(&s1, sn+1, &mem);
//   walloc1d(&s2, sn+1, &mem);
//   walloc1d(&isp, sn+1, &mem);
// 
//   s1[0] = 0;
//   rep(i,1,sn+1) s1[i] = ((T)i) * ((T)(i+1)) / 2 - 1;
//   rep(i,1,sn+1) s2[i] = ((T)(n/i)) * ((T)(n/i+1)) / 2 - 1;
//   rep(i,2,sn+1) isp[i] = 1;
// 
//   rep(i,2,ssn+1) if(isp[i]){
//     for(j=i*i;j<=sn;j+=i) isp[j] = 0;
//     rep(j,1,sn+1){
//       x = (ll) i * j;
//       if(x > sn) s2[j] -= i * (s1[(int)(nn / x)] - c);
//       else       s2[j] -= i * (s2[x] - c);
//     }
//     for(k = (sn+1)/i; k >= i; k--){
//       m = min(sn+1, i*(k+1));
//       tmp = i * (s1[k] - c);
//       rep(j,i*k,m) s1[j] -= tmp;
//     }
//     c += i;
//   }
// 
//   rep(i,ssn+1,sn+1) if(isp[i]){
//     rep(j,1,sn+1){
//       x = (ll) i * j;
//       if(x * i > n) break;
//       if(x > sn) s2[j] -= i * (s1[(int)(nn / x)] - c);
//       else       s2[j] -= i * (s2[x] - c);
//     }
//     c += i;
//   }
// 
//   return s2[1];
// }
// 
// {
//   ll L, R;
//   L = cReader_ll(1, 1d10, ' ');
//   R = cReader_ll(L, 1d10, '\n');
//   cReader_eof();
//   wt(cntPrime(2*R) - cntPrime(2*L) + cntPrime(R) - cntPrime(L-1));
// }