factorial n = factorial_helper 1 n
factorial_helper prod 0 = prod
factorial_helper prod n = factorial_helper (prod*n) (n-1)
main
= print (factorial
5)
ZmFjdG9yaWFsIG4gPSBmYWN0b3JpYWxfaGVscGVyIDEgbgoKZmFjdG9yaWFsX2hlbHBlciBwcm9kIDAgPSBwcm9kCmZhY3RvcmlhbF9oZWxwZXIgcHJvZCBuID0gZmFjdG9yaWFsX2hlbHBlciAocHJvZCpuKSAobi0xKQoKCm1haW4gPSBwcmludCAoZmFjdG9yaWFsIDUp