Given jugs with capacities 4, 8 and 20, target 1 is not achievable. Given jugs with capacities 4, 8 and 20, target 2 is not achievable. Given jugs with capacities 4, 8 and 20, target 3 is not achievable. Given jugs with capacities 4, 8 and 20, target 4 is achievable using 4 gallons of water. Given jugs with capacities 4, 8 and 20, target 5 is not achievable. Given jugs with capacities 4, 8 and 20, target 6 is not achievable. Given jugs with capacities 4, 8 and 20, target 7 is not achievable. Given jugs with capacities 4, 8 and 20, target 8 is achievable using 8 gallons of water. Given jugs with capacities 4, 8 and 20, target 9 is not achievable. Given jugs with capacities 4, 8 and 20, target 10 is not achievable. Given jugs with capacities 4, 8 and 20, target 11 is not achievable. Given jugs with capacities 4, 8 and 20, target 12 is achievable using 12 gallons of water. Given jugs with capacities 4, 8 and 20, target 13 is not achievable. Given jugs with capacities 4, 8 and 20, target 14 is not achievable. Given jugs with capacities 4, 8 and 20, target 15 is not achievable. Given jugs with capacities 4, 8 and 20, target 16 is achievable using 16 gallons of water. Given jugs with capacities 4, 8 and 20, target 17 is not achievable. Given jugs with capacities 4, 8 and 20, target 18 is not achievable.