#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,x,mx=0;
	cin>>a>>b>>x;
	for(int i=b;i<=x;i++){
		if(i%a>mx){
			mx=i%a;	
		} 
	}cout<<mx;
}
/**************************************************************
	Problem: 2401
	User: panyuchen
	Language: C++
	Result: Time Limit Exceed
****************************************************************/