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namespace eloi {
template <unsigned long N, unsigned long Lo = 1, unsigned long Hi = N>
struct Sqrt {
enum {
median = Lo + (Hi - Lo + 1) / 2,
is_left = N < median * median,
new_lo = is_left ? Lo : median,
new_hi = is_left ? median - 1 : Hi,
value = Sqrt<N, new_lo, new_hi>::value
};
};
template <unsigned long N, unsigned long M>
struct Sqrt<N, M, M> { enum { value = M }; };
}
template <bool> struct enforce;
template <> struct enforce<true> { };
template <unsigned long N>
struct check {
enum {
x = sizeof(enforce<(eloi::Sqrt<N * N - 1>::value == N - 1)>),
y = sizeof(enforce<(eloi::Sqrt<N * N>::value == N)>),
z = sizeof(enforce<(eloi::Sqrt<N * N + 1>::value == N)>),
valid = check<N - 1>::valid
};
};
template <>
struct check<1> {
enum { valid = true };
};
template struct check<50>;
int main () { return 0; }
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