49 lines
1.0 KiB
C++
49 lines
1.0 KiB
C++
//http://contest-hunter.org:83/contest/0x10%E3%80%8C%E5%9F%BA%E6%9C%AC%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84%E3%80%8D%E4%BE%8B%E9%A2%98/1102%20%E7%81%AB%E8%BD%A6%E8%BF%9B%E5%87%BA%E6%A0%88%E9%97%AE%E9%A2%98
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#include<cstdio>
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#include<cstring>
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#include<algorithm>
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#include<vector>
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using namespace std;
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const int maxn=60005;
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int n,p[maxn*2],isp[maxn*2],res[1000005]={0,1},len=1,pcnt;
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inline void times(int x)
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{
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for(int i=1;i<=len;i++) res[i]*=x;
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len+=6;
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for(int i=1;i<=len;i++)
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{
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res[i+1]+=res[i]/10;
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res[i]%=10;
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}
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while(!res[len]) len--;
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}
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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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scanf("%d",&n);
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memset(isp,1,sizeof(isp)); isp[0]=isp[1]=0;
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for(int i=2;i<=n*2;i++)
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{
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if(isp[i]) p[pcnt++]=i;
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for(int j=0;j<pcnt&&p[j]*i<=n*2;j++)
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{
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isp[p[j]*i]=0;
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if(i%p[j]==0) break;
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}
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}
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for(int i=0;i<pcnt;i++)
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{
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int a=p[i],acnt=0;
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while(a<=n*2)
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{
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acnt+= n*2/a - n/a - (n+1)/a;
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a=a*p[i];
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}
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while(acnt--) times(p[i]);
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}
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for(int i=len;i>=1;i--) printf("%d",res[i]); puts("");
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return 0;
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}
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