A2.cc

/* |\ _,,,---,,_ /,`.-'`' -. ;-;;,_ |,4- ) )-,_..;\ ( `'-' '---''(_/--' `-'\_) Meow do you do ヽ(●´∀`●)ﾉ */ #include <iostream> using namespace std; string ans[99] = {"1.5000000000","2.2500000000","3.2142857143","4.4857142857","6.2198156682","8.6467357911","12.1044437994","17.0919352918","24.3495977585","34.9794609867","50.6250205168","73.7403531089","107.9931336733","158.8684407298","234.5736341956","347.3946774734","515.7294029045","767.1359025981","1142.9032392550","1704.9051738955","2545.8778387887","3804.8326026100","5690.1708170717","8514.3502525070","12745.8776507802","19087.2886845923","28592.1068150030","42840.2677327342","64201.2387214846","96228.6760880450","144252.3842983191","216266.2209304368","324259.9119275476","486216.7217690962","729109.8928576226","1093397.2222779050","1639762.8240529624","2459229.6439455855","3688328.0709560286","5531848.6537141928","8296970.9240296409","12444456.3184521488","18665437.1684444632","27996599.6954735396","41992957.8909849014","62987013.5705894886","94477495.4981854391","141712466.8757602598","212563985.0826939889","318840089.4155497052","478252780.3613993146","717369985.5874707768","1076043505.2753130479","1614050925.5592975888","2421058482.9810934909","3631565354.0424531356","5447320080.6234268696","8170945196.9712092165","12256374156.2605340582","18384506703.0309805769","27576691910.0891238175","41364952706.6698331005","62047322636.6886988808","93070850953.6343493685","139606110209.7992065787","209408957573.7418558536","314113176723.5015302400","471169440582.6962486294","706753755295.0167143912","1060130126023.9020641909","1590194555449.4711446096","2385291041260.6945219055","3577935572077.1254869258","5366902120935.8237072747","8050351635027.1844453539","12075525519680.4443197928","18113285863569.1840354313","27169925775553.6236092455","40754884888736.6012109270","61132322615038.2665896045","91698478025171.4139079021","137547709666246.4048017938","206321555285230.3322873758","309482321410451.3686731824","464223467719249.0272525647","696335183583692.0617410352","1044502752881958.9061182190","1566754101206410.8798775570","2350131116664459.4133422455","3525196631065806.9016185778","5287794891685742.9156400699","7931692268888118.2003303146","11897538317532359.8670808671","17846307369049668.7561912004","26769460919514430.2726985396","40154191211697689.1745508614","60231286608080375.2999966820","90346929650289309.7178481716","135520394148146523.1726908779"}; int main() { ios::sync_with_stdio(false); int n; cin >> n; cout<<ans[n-2]<<endl; return 0; }