#include<stdio.h>
#include<iostream>
using namespace std;
int main()
{
int min,max,flag,count=0,j=0;
int a[20];
cin>>min;
cin>>max;
while(min<max){
flag = 0;
for(int i=2;i<=min/2;i++){
if(min%i==0){
flag = 1;
break;
}
}
if(flag == 0){
count++;
while(count>0){
a[j]=min;
j++;
}
}
min++;
}
for(int i=0;i<count;i++){
cout<<a[i];
}
return 0;
}
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