#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MAX 10005
#define MAX1 100005
int main()
{
ll a,b,n;
cin>>a>>b>>n;
ll count=0;
ll div[MAX];
bool prime[MAX1];
//memset(div,2,sizeof(div));
for(ll i=0; i<=(b-a+2); i++)
div[i]=2;
memset(prime,true,sizeof(prime));
clock_t start,end;
start=clock();
for(ll p=2; p*p<=b; p++)
{
for(ll i=p*2; i<=b; i+=p)
{
if(a<=i && i<=b)
{
ll m=i-a;
div[m]++;
//cout<<"L";
//cout<<"Hi";
}
}
}
if(a==1)
{
div[0]=1;
}
for(int i=0; i<=(b-a); i++)
{
if(div[i]==n)
{
//cout<<i<<" ";
count++;
}
}
cout<<count;
end=clock();
//cout<<(float)(end-start)/CLOCKS_PER_SEC;
}
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