prog.cpp: In function 'int main()':
prog.cpp:27:35: error: invalid use of incomplete type 'struct sum_from<1ull>::to<250000ull>::result'
prog.cpp:20:12: error: declaration of 'struct sum_from<1ull>::to<250000ull>::result'
g++: Internal error: Segmentation fault (program cc1plus)
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