PROGRAMMING:When is the short position

The existing goods in a warehouse are $$s $$boxes, which are shipped in the morning and purchased in the afternoon. If $$s / GEQ M / GT n / GEQ 0 $$, there will be an empty position on the day of $$k $$. Please help the warehouse administrator write a program, input $$s $, $$M $$and $$n $$, calculate and output $$k $$.
####Input format
> $$s, m, n (s \geq m \gt n \geq 0)$$
####Output format
> $$k$$
####Input sample
```in
10 5 2
```
####Output sample
```out
three
```







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