int ntrig;
int tmp;

double R1;
double R2;

double XN;
double XN1;
double YN;
double YN1;
double XCR1;
double XCR2;

int x;
int y;
double rem;
int n;

ntrig = 0;
tmp = 0;

R1 = 3.990;
R2 = 3.984;

XN = 0.400;
XN1 = 0.800;
YN = 0.500;
YN1 = 0.720;
XCR1 = 0.496;
XCR2 = 0.477;

n = 1;

if ((inlet_trig > 0) && !ntrig) {

  ntrig = 1;

  if ((XN < XCR1) && (XN1 >= XCR1))
    x = 0;
  if ((XN >= XCR1) && (XN1 < XCR1))
    x = 1;
  if ((YN < XCR2) && (YN1 >= XCR2))
    y = 0;
  if ((YN >= XCR2) && (YN1 < XCR2))
    y = 1;

  rem = n % 2;

  if (rem == 1.00) {

    if ((x == 0) && (y == 0))
      tmp = 0;
    if ((x == 1) && (y == 1))
      tmp = 0;
    if ((x == 0) && (y == 1))
      tmp = 1;
    if ((x == 1) && (y == 0))
      tmp = 1;
  }

  XN = XN1;
  XN1 = R1 * XN * (1.000 - XN);
  YN = YN1;
  YN1 = R2 * YN * (1.000 - YN);

  n = n + 1;

} else if (!(inlet_trig > 0))
  ntrig = 0;

outlet_gate = tmp;
disp_gate = tmp;