void main(){
  import std.stdio, std.string, std.conv, std.algorithm;
  
  int a, b, c; rd(a, b, c);
  
  int[int] cnt;
  cnt[a]=1;
  if(b in cnt) writeln(c);
  else if(c in cnt) writeln(b);
  else writeln(a);
}

void rd(T...)(ref T x){
  import std.stdio, std.string, std.conv;
  auto l=readln.split;
  foreach(i, ref e; x){
    e=l[i].to!(typeof(e));
  }
}