#include <bits/stdc++.h>

using namespace std;

#define endl '\n'

#define TRACE 1
#define tcout TRACE && cout

#define fst ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);

#define int long long

#define big string
#define bigcin getline

const int P = 998244353;
const int INF = 0x3f3f3f3f3f3f3f3f;
const int N = 1e13 + 10, M = 2e6 + 10;

int a[10];
signed main()
{
	long long a,b,c;
	cin >> a >> b >> c;
	if(a>b)
	{
		swap(a,b);
	}
	if(b>c)
	{
		swap(b,c);
	}
	if(a+b<c)
	{
		cout << -1;
		return 0;
	}
	cout << c;
	return 0;
}//做好事不留名,我叫陈一墨