#include<stdio.h>
float deal(float k,float xy[])
{
if( xy[0] > xy[1] )
{
float t = xy[0];
xy[0] = xy[1];
xy[1] = t;
}
if( xy[2] > xy[3] )
{
float t = xy[2];
xy[2] = xy[3];
xy[3] = t;
}
if( xy[1] <= xy[3] )
{
if( xy[1] <= xy[2] )
{
return 0;
}
else
{
if( xy[0] > xy[2] )
{
return xy[1] - xy[0];
}
else
{
return xy[1] - xy[2];
}
}
}
else
{
if( xy[3] <= xy[0] )
{
return 0;
}
else
{
if( xy[2] >= xy[0] )
{
return xy[3] - xy[2];
}
else
{
return xy[3] - xy[0];
}
}
}
}
int main()
{
float x[4],y[4];
while(scanf("%f%f",&x[0],&y[0]) == 2 )
{
int i;
for( i = 1; i < 4; i++ )
{
scanf( "%f%f", &x[i], &y[i] );
}
float len = deal( len, x );
float wid = deal( wid, y );
printf( "%.2f\n", len*wid );
}
return 0;
}