#include<stdio.h> int main(){ int a=2,b=1,c,n,i; double s=0; scanf("%d",&n); if(n>10||n<1)return 0; for (i=1;i<=n;i ++) { s+=(1.0*a/b); c=b; b=a; a=a+c; } printf("%.6f\n",s); return 0; }
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