include<bits/stdc++.h>

using namespace std;

int main() {

int A,B,D,c=0;
cin>>A>>B>>D;
for(int n=A;n<=B;n++){
    bool p=1;
    if(n<2)p=0;
    if(n>2&&n%2==0)p=0;
    for(int i=3;p&&i*i<=n;i+=2)if(n%i==0)p=0;
    if(!p)continue;
    int t=n;
    while(t){
        if(t%10==D){c++;break;}
        t/=10;
    }
}
cout<<c;
return 0;

}