#include<bits/stdc++.h>
using namespace std;
int a[5], minn = 1e9, maxx = -1e9, cnt;
int main() {
	for (int i = 1; i <= 3; i++) {
		cin >> a[i];
	}
	sort(a + 1, a + 3 + 1);
	for (int i = 1; i <= 3 + 1; i++) {
		minn = min(abs(a[i] - a[i + 1]), minn);
		maxx = max(abs(a[i] - a[i + 1]), maxx);
		if (maxx == abs(a[i] - a[i + 1]) && minn == maxx) {
			cnt = abs(a[i] - a[i + 1]);
		}
	}
	cout << a[3] + cnt;
	return 0;
}