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Ruby, 8 13 operations
def tetr(a, b)
def exp(a, b)
def mult(a, b)
c = 0; i = 0; while(i > -b) do c -= a; i -= 1; end
return -c
end
c = 1; i = 0; while(i > -b) do c = mult(c, a); i -= 1; end
return c
end
c = a; i = -1; while(i > -b) do c = exp(a, c); i -= 1; end
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