import std.functional,
       std.algorithm,
       std.container,
       std.typetuple,
       std.typecons,
       std.bigint,
       std.string,
       std.traits,
       std.array,
       std.range,
       std.stdio,
       std.conv,
       std.format,
       std.math;

void main()
{
	auto ip = readln.split.to!(int[]), a=ip[0], b=ip[1], c=ip[2];
	if(a==b) writeln(c);
	else if(b==c) writeln(a);
	else writeln(b);
}