#include <bits/stdc++.h>
using namespace std;
const long long N = 1000005;
const long long M = 1000000007;
long long n, m, cc, len;
long long s[5];
int main() {
  long long sum = 0;
  for (long long i = 0; i < 3; i++) scanf("%I64d", &s[i]), sum += s[i];
  sort(s, s + 3);
  long long ans = -1;
  for (long long i = 0; i < 3; i++)
    for (long long j = i + 1; j < 3; j++) {
      long long ano = sum - s[i] - s[j];
      if ((s[i] + s[j]) % 2 == 0 && ano >= (abs(s[j] - s[i]) / 2)) {
        if (ans == -1) ans = s[j];
        ans = min(ans, s[j]);
      }
    }
  if (ans == -1) ans = s[2];
  printf("%I64d\n", ans);
  return 0;
}
