```
list1 = [(1533945600000, 140), (1534032000000, 412), (1534118400000, 364), (1534204800000, 488), (1534291200000, 272), (1534377600000, 350), (1534464000000, 301), (1534550400000, 159), (1534636800000, 224), (1534723200000, 241), (1534809600000, 223), (1534896000000, 175)]

list2 = [(1533945600000, 1516), (1534032000000, 2176), (1534118400000, 2046), (1534204800000, 2400), (1534291200000, 8370), (1534377600000, 2112), (1534464000000, 1441), (1534550400000, 784), (1534636800000, 1391), (1534723200000, 1178), (1534809600000, 1020), (1534896000000, 795)]

```

How could you combine them into a single list of tuples? considering the first value of the key appears in both lists.