#include<cstdio> #include<cstring> #include<cmath> using namespace std; int map[110][110]; int main(){ int a,b,c; int i,j,k; int x,y; int x2,y2; int x3,y3; double sum1,sum2; double sum; while(scanf("%d",&a)!=EOF){ sum=0.0; x=2; x2=3; y=1; y2=2; if(a==1){ printf("2.00\n"); } else if(a==2){ printf("3.50\n"); } else{ sum=3.5; for(i=0;i<a-2;i++){ x3=x+x2; x=x2; x2=x3; y3=y+y2; y=y2; y2=y3; sum1=(double)x3; sum2=(double)y3; sum=sum+(sum1/sum2); } printf("%.2lf\n",sum); } } return 0; } |
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