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

void main(){
  auto buf = readln().strip().split().map!(to!int)().array;

  int maxe = max(buf[0], buf[1]);
  int mine = min(buf[0], buf[1]);

  int d = buf[2];

  if(d > maxe) {
    d = maxe + mine - d;
  } else if(d > mine) {
    d = mine;
  }

  if(d < 0) {
    writeln(0);
  } else {
    writeln(d+1);
  }
}