#include <bits/stdc++.h>
using namespace std;
long long a, b, c;
long long Ans = -1;
inline void ReNew(long long& Ans, long long x) {
  if (Ans > x || Ans == -1) Ans = x;
}
int main() {
  scanf("%I64d%I64d%I64d", &a, &b, &c);
  if (a == b)
    ReNew(Ans, a);
  else if (b == c)
    ReNew(Ans, b);
  else if (a == c)
    ReNew(Ans, c);
  if (a < b) swap(a, b);
  if (a < c) swap(a, c);
  if (b < c) swap(b, c);
  if (!((a - b) & 1)) ReNew(Ans, a);
  if (!((b - c) & 1)) ReNew(Ans, b);
  if (!((a - c) & 1)) ReNew(Ans, a);
  cout << Ans;
  return 0;
}
