#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>

#include <functional>
#include <cassert>

typedef long long ll;
using namespace std;

#define debug(x) cerr << #x << " = " << x << endl;


#define mod 1000000007 //1e9+7(prime number)
#define INF 1000000000 //1e9
#define LLINF 2000000000000000000LL //2e18
#define SIZE 10000


int main(){
  int n;
  ll a, b;
  ll ans = LLINF;
  
  scanf("%lld%lld%d",&a,&b,&n);

  for(int i=1;i<=n;i++){
    for(int j=1;j<=n;j++){
      // i : j

      if(b%j) continue;

      ans = min(abs(a - (b/j)*i),ans);
    }
  }

  printf("%lld\n",ans);
  
  return 0;
}