import core.bitop;
import std.algorithm;
import std.ascii;
import std.bigint;
import std.conv;
import std.functional;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.random;
import std.typecons;

alias sread = () => readln.chomp();
alias Point2 = Tuple!(long, "y", long, "x");

T lread(T = long)()
{
    return readln.chomp.to!T();
}

T[] aryread(T = long)()
{
    return readln.split.to!(T[])();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}

void minAssign(T, U = T)(ref T dst, U src)
{
    dst = cast(T) min(dst, src);
}

void maxAssign(T, U = T)(ref T dst, U src)
{
    dst = cast(T) max(dst, src);
}

void main()
{
    long A, B, C;
    scan(A, B, C);

    if (A == B)
    {
        C.writeln();
    }
    else if (A == C)
    {
        B.writeln();
    }
    else
    {
        A.writeln();
    }
}
