Last summer, Sheila decided to measure change in a swimming pool's

water level each week. There was a hot and dry spell that lasted 4

weeks and the water level dropped the following amounts each week

Sheila measured the level: 8 millimeters in the first week, 5 millimeters

in the second week, 12 millimeters in the third week, and 5 millimeters

in the fourth week. Express the total gain/loss of water over the 4

weeks as an integer