Description

Yesterday, a kindergarten child found $3$ small stones and wants to pick up one more stone so that the total weight of the $4$ stones is exactly $20$ pounds. What should be the weight of the stone he should pick up?

Input Format

Three integers $a$, $b$, $c$, representing the weights of the three stones (in pounds). ($0 < a,b,c,a+b+c \le 20$)

Output Format

An integer representing the weight of the fourth stone (in pounds).

Sample

3 5 7

5