C++ :

#include<bits/stdc++.h>
using namespace std;
int work(int x,int y)
{
	int c=x%y,ans=0;	
	if(c==0) ans=0;
	else   ans=(x/y+1)*y-x;
	return ans;
}
int n,a,b;
int main()
{
//	freopen("1016.in","r",stdin);
//	freopen("1016.out","w",stdout);	
	cin>>n>>a>>b;
	int a1=work(n,a),b1=work(n,b);
	cout<<min(a1,b1);
	return 0;
}