import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string;

void readA(T)(size_t n,ref T[]t){t=new T[](n);auto r=readln.splitter;foreach(ref v;t){v=r.front.to!T;r.popFront;}}

void main()
{
  int[] a; readA(3, a);
  a.sort();
  writeln(a[0] == a[1] ? a[2] : a[0]);
}
