Football field is a kind of sports venue for football games. It is a rectangular space surrounded by four white lines and two long lines in the middle. The length of the field is between 100 and 110 yards， and the width is between 50 and 100 yards. The lines on the field are white and each line is 5 inches wide. The center line divides the field into two halves， and each of the two halves is a penalty area. The penalty area is marked with a white line and a semicircle in the penalty area. On each side of the penalty area， there is a goal post， and the goal post is made of wood and metal. Outside the penalty area is the sideline， which is also marked with a white line. The penalty mark is placed at the penalty area， and the penalty mark is 12 yards away from the center line. In the middle of the field is a circle with a radius of 10 yards， which is the center circle.
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