```
template <class M, class N>
constexpr common_type_t<M,N> lcm(M m, N n);
```

Requires: |m| and |n| shall be representable as a value of common_type_t<M, N>. The least common multiple of |m| and |n| shall be representable as a value of type common_type_t<M,N>.

Remarks: If either M or N is not an integer type, or if either is cv bool the program is ill-formed.

Returns: Zero when either m or n is zero. Otherwise, returns the least common multiple of |m| and |n|.