17 lines
199 B
C++
17 lines
199 B
C++
#include<cstdio>
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using namespace std;
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int main()
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{
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int n;
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double ans=0;
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scanf("%d",&n);
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for(int i=1;i<=n;i++)
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{
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if(i&1) ans+=1.0/i;
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else ans-=1.0/i;
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}
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printf("%.4lf\n",ans);
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return 0;
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}
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