21 lines
391 B
C++
21 lines
391 B
C++
#include<cstdio>
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const int maxn=50000;
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int n,i,j,phi[maxn+5],sum[maxn+5];
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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phi[1]=1;
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for(i=2;i<=maxn;i++)
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if(!phi[i])
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for(j=i;j<=maxn;j+=i)
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{
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if(!phi[j]) phi[j]=j;
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phi[j]=phi[j]/i*(i-1);
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}
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for(i=1;i<=maxn;i++) sum[i]=sum[i-1]+phi[i];
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while(scanf("%d",&n)==1&&n) printf("%d\n",2*(sum[n]-1)+1);
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return 0;
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}
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