Answer:
25
Explanation:
Let n be the first integer. 
Then the second integer will be (n + 1). 
And the third will be (n + 2). 
The sum is 78. Therefore: 

Solve for n. Combine like terms: 

So: 

Therefore: 

Therefore, the first integer is 25. 
So our sequene is 25, 26, and 27. 
The integer closest to zero will thus be 25.