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

void main()
{
    auto input = readln.split.to!(ulong[]);
    auto F0 = input[0], F1 = input[1], N = input[2];

    recurrence!"a[n-1]^a[n-2]"(F0, F1).take(N % 3 + 1).array.back.writeln;
}