19 lines
256 B
C++
19 lines
256 B
C++
#include<cstdio>
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using namespace std;
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bool isp(int n)
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{
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if(!n&1) return 0;
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for(int i=2;i*i<=n;i++) if(n%i==0) return 0;
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return 1;
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}
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int main()
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{
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int ans=1;
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int n;
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scanf("%d",&n);
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for(int i=3;i<=n;i++) ans+=isp(i);
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printf("%d\n",ans);
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return 0;
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}
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