I want to add those 3 numbers on excel but when i am using the sum function and drag the cells its also considering the numbers inbetween cells 50 and 104. how can i fix this problem?

Note: there's alot of numbers that i want add therefore selecting them individually will be time consuming.

the cells are already under each other it's just that the cell numbers are different and i want to add them together.

how can i add them in a time efficent manner?

50 104 105 50 104 105