21
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It does not matter what you put after this. This will not be read.

the song is 5.142 seconds long.
5.142 ~ 5.25
5.142 is close to 5.25 seconds (or 20 + 1 quater seconds)

Figure out how many quarter seconds are there in 5.25 seconds
5 * 4 = 20
0.25/0.25 = 1;

20 + 1 = 21

Once you figure out how many quarter seconds there are in your song you put that number as the first line. 
Note: it can not have any decimal points.