#include <stdio.h>
#include <stdlib.h>

/*
 *На входе спираль в двумерном массиве(spiral,m,n), указатели на текущее положение в спирали(i,j),
 *статус движения с пирали: 0-вправо,1-вниз,2-влево,3-вверх
 *Функция изменяет значения текущего положения в спирали(i,j), 
 *при необходимости изменяется статус движения. Устанавливает уже пройденные значения в 1.
 *При успешном завершении функции возвращается 0.
 */
int move_on_square_spiral(int* s, int n, int m, int* cur_i, int* cur_j, int* cur_state)
{
	int i = *cur_i;
	int j = *cur_j;
	int state = *cur_state % 4;

	if (state == 0) //вправо
	{
		if (j < m-1 && s[i*m + j + 1]!= 1)
		{
			s[i*m + j + 1] = 1;
			*cur_j += 1;
		}
		else
		{
			s[(i + 1)*m + j]=1;
			*cur_i += 1;
			*cur_state += 1;
		}
	}
	else if (state==1)//вниз
	{
		if (i < n-1 && s[(i+1)*m+j] != 1)
		{
			s[(i + 1)*m + j]=1;
			*cur_i += 1;
		}
		else
		{
			s[i*m + j-1] = 1;
			*cur_j -= 1;
			*cur_state += 1;
		}
	}
	else if (state == 2)//влево
	{
		if (j > 0 && s[i*m+j-1] != 1)
		{
			s[i*m + j - 1] = 1;
			*cur_j -= 1;
		}
		else
		{
			s[(i - 1)*m + j] = 1;
			*cur_i -= 1;
			*cur_state += 1;
		}
	}
	else if (state == 3)//вверх
	{
		if (i > 0 && s[(i-1)*m+j] != 1)
		{
			s[(i - 1)*m + j] = 1;
			*cur_i -= 1;
		}
		else
		{
			s[i*m + j+1] = 1;
			*cur_j += 1;
			*cur_state += 1;
		}
	}
	return 0;
}

int main(int argc, char** argv)
{
	FILE* in = fopen("input.txt", "r");
	if (!in)
	{
		printf("File 'input.txt' not found.\n");
		return 0;
	}

	//чтение и запись входных параметров
	int n, m;
	int end_i, end_j;
	fscanf(in, "%i %i", &n, &m);
	fscanf(in, "%i %i", &end_i, &end_j);
	fclose(in);

	end_i -= 1;
	end_j -= 1;

	//инициализация спирали
	int* a = (int*)calloc(n*m, sizeof(int));
	a[0] = 1;

	//основная часть
	int res = 1;
	int cur_i = 0, cur_j = 0;
	int cur_state = 0;

	while (!(cur_i==end_i && cur_j==end_j))
	{
		move_on_square_spiral(a, n, m, &cur_i, &cur_j, &cur_state);
		res += 1;
	}

	FILE* out = fopen("output.txt", "w");
	fprintf(out, "%i", res);
	fclose(out);
	
	return 0;

}

function CellCount1(M, N, X, Y: integer): integer;
var
  Top, Right, Bottom, Left, Direction, LoopCount: integer;
begin;
  Top:=Y-1; Right:=M-X; Bottom:=N-Y; Left:=X-1;
  LoopCount:=Top; DiRection:=0;
  if LoopCount>Right then begin; LoopCount:=Right; Direction:=1; end;
  if LoopCount>Bottom then begin; LoopCount:=Bottom; Direction:=2; end;
  if LoopCount>Left then begin; LoopCount:=Left; Direction:=3; end;
  Result:=0;
  if LoopCount>0 then Result:=2*(M+N-2*LoopCount)*LoopCount;
  if Direction=0 then Result:=Result+X-LoopCount
  else begin;
    Result:=Result+M-2*LoopCount-1;
    if Direction=1 then Result:=Result+Y-LoopCount
    else begin;
      Result:=Result+N-2*LoopCount-1;
      if Direction=2 then Result:=Result+M-LoopCount-X+1
      else begin;
        Result:=Result+M-2*LoopCount-1;
        Result:=Result+N-LoopCount-Y+1;
        end;
      end;
    end;
  end;

function CellCount2(M, N, X, Y: integer): integer;
var
  Top, Right, Bottom, Left, Direction, LoopCount: integer;
begin;
  Top:=Y-1; Right:=M-X; Bottom:=N-Y; Left:=X-1;
  LoopCount:=Top; DiRection:=0;
  if LoopCount>Right then begin; LoopCount:=Right; Direction:=1; end;
  if LoopCount>Bottom then begin; LoopCount:=Bottom; Direction:=2; end;
  if LoopCount>Left then begin; LoopCount:=Left; Direction:=3; end;
  Result:=0;
  if LoopCount>0 then Result:=2*(M+N-2*LoopCount)*LoopCount;
  case Direction of
    0: Result:=Result+X-LoopCount;
    1: Result:=Result+Y-3*LoopCount+M-1;
    2: Result:=Result-X-5*LoopCount+2*M+N-1;
    3: Result:=Result-Y-7*LoopCount+2*M+2*N-2;
    end;
  end;

  if LoopCount>0 then Result:=2*(M+N-2*LoopCount)*LoopCount;
  case Direction of
    0: Result:=Result+X-LoopCount;
    1: Result:=Result+Y-3*LoopCount+M-1;
    2: Result:=Result-X-5*LoopCount+2*M+N-1;
    3: Result:=Result-Y-7*LoopCount+2*M+2*N-2;
    end;
  end;