#include <iostream>
#include <cstring>
using namespace std;
int fun(int n);
int n, m, k;
int a[700010];
int p[110];
int main()
{
for(int i = 1; i <= 700000; i++)
{
if(fun(i))
a[i] = 1;
}
while(cin >> n >> m >> k, m+n+k)
{
memset(p, 0, sizeof(p));
int num = 1;
while(p[m] < k)
{
for(int i = 1; i <= n && p[m] < k; i++, num++)
{
if(a[num])
p[i]++;
}
for(int i = n-1; i >= 2 && p[m] < k; i--, num++)
{
if(a[num])
p[i]++;
}
}
cout << --num << endl;
}
}
int fun(int n)
{
if(n % 7 == 0)
return 1;
while(n)
{
int t;
t = n % 10;
n = n / 10;
if(t == 7)
return 1;
}
return 0;
}