45 lines
813 B
C++
45 lines
813 B
C++
#include<cstdio>
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typedef long long LL;
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inline int K(int x)
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{
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int k=0; for(;(1<<k)<=x;++k);
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return k;
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}
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LL n,res,mxgs;
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const int p[16]={1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47};
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int limit_p[16],p1;
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void dfs(LL i,LL gs,LL num,LL mxq)
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{
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if(num>n) return;
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if(i>1) limit_p[i]=p1/(K(p[i])-1)+1;//ceil((p1+1)/(K(p[i])-1))
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LL val=num*p[i],q=1,ngs=gs;
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while(q<limit_p[i]&&q<=mxq&&val<=n)
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{
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ngs=gs*(q+1);
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if(ngs>mxgs) mxgs=ngs,res=val;
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if(ngs==mxgs&&val<res) res=val;
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if(i==1) p1=q;
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dfs(i+1,ngs,val,q);
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val*=p[i],++q;
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}
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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("%lld",&n);
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if(n==1) { printf("1\n"); return 0; }
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res=mxgs=1;
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LL x=1,t=0;
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for(int i=1;i<16&&x<=n;++i) x*=p[i],t=i;
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t=K(p[t])*2-1;
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limit_p[1]=t;
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dfs(1,1,1,20);
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printf("%lld\n",res);
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return 0;
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}
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