import std.stdio;
import std.string;
import std.conv;
import std.bigint;
import std.typecons;
import std.algorithm;
import std.array;
import std.math;
import std.range;
 
void main() {
    auto tmp = readln.split.to!(int[]);
    if (tmp[0] == tmp[1]) writeln(tmp[2]);
    else if (tmp[1] == tmp[2]) writeln(tmp[0]);
    else writeln(tmp[1]);
}
