/*
TASK: rprimes
LANG: C++
*/
#include<stdio.h>
int j[72]={2,3,5,7,23,29,31,37,53,59,71,73,79,233,239,293,311,313,317,373,379,593,599,719,733,739,797,2333,2339,2393,2399,2939,3119,3137,3733,3739,3793,3797,5939,7193,7331,7333,7393,23333,23339,23399,23993,29399,31193,31379,37337,37339,37397,59393,59399,71933,73331,73939,233993,239933,293999,373379,373393,593933,593993,719333,739391,739393,739397,739399};
int main ()
{
    int a,b,i,br=0;
    scanf("%d%d",&a,&b);
    for(i=0;i<45;i++)
    {
      if(j[i]>=a&&j[i]<=b)br++;
     } 
  printf("%d\n",br);
    return 0;
    }

