import std.algorithm, std.array, std.container, std.range;
import std.string, std.conv;
import std.math, std.bigint, std.bitmanip, std.random;
import std.stdio, std.typecons;

void main()
{
  auto rd = readln.split.map!(to!int);
  auto a = rd[0], b = rd[1], s = rd[2];

  if (s == 1) {
    if (a == 0)
      writeln(2);
    else
      writeln(a);
  } else if ((s - a).abs <= (s - b).abs) {
    writeln((s - a).abs + s);
  } else {
    if ((s - a).abs <= s - 1)
      writeln((s - b).abs + (s - a).abs + a);
    else if (a == 0)
      writeln((s - b).abs + s - 1 + 2);
    else
      writeln((s - b).abs + s - 1 + a);
  }
}