#include <stdio.h>
#define N 1024

float x[N+2][N+2][2];

#define myabs(a) (((a) > 0) ? (a):(-(a)))

int main(void) 
{
  float a1, a2, a3, a4, a5, a6;
  float MAXDIFF;
  int i, j;
  int t, t1, t2;
  float  maxdiff1;
  int iteration;

  /*
  scanf("%f %f %f %f %f %f %f", &a1, &a2, &a3, &a4, &a5, &a6, &MAXDIFF);
  */
  
  a1 = a2 = a3 = a4 = 0.25; a6 = 0; a5 = 0.1;

  MAXDIFF = 0.0001;

  printf("maxdiff = %13.12f\n", MAXDIFF);

  for (i=1; i<=N+1; i++) {
    x[i][0][0] = 0.0;
    x[i][0][1] = 0.0;

    x[i][N+1][0] = 0.0;
    x[i][N+1][1] = 0.0;

    x[0][i][0] = a5*i;
    x[0][i][1] = a5*i;

    x[N+1][i][0] = a6*i;
    x[N+1][i][1] = a6*i; 
  }


  for (i=1; i<=N; i++) 
    for (j=1; j<=N; j++) {
      x[i][j][0] = 0.0;
      x[i][j][1] = 0.0;
    }

  printf("maxdiff=%13.12f\n", MAXDIFF);

  t = 0; t1 = 1;
  maxdiff1 = 1.0;
  iteration = 0;

  while (maxdiff1 > MAXDIFF) {
    maxdiff1 = -1.0;
    for (i=1; i <= N; i++) 
      for (j=1; j <=N; j++) {
        x[i][j][t] = a1*x[i-1][j][t1] + a2 * x[i+1][j][t1] +
	             a3*x[i][j-1][t1] + a4 * x[i][j+1][t1];
	if (myabs(x[i][j][t] - x[i][j][t1]) > maxdiff1)
	  maxdiff1 = myabs(x[i][j][t] - x[i][j][t1]);
      }

    t2 = t; t = t1; t1 = t2;
    printf("iteration = %d, maxdiff1 = %f, MAXDIFF = %f\n", 
           iteration++, maxdiff1, MAXDIFF);
  }
    printf("MAXDIFF = %f, maxdiff = %f\n", MAXDIFF, maxdiff1);
}