Time Limit:3000MS Memory Limit:0KB 64bit IO Format:%lld & %llu
又是素数:
#include<cstdio>
#include<algorithm>
#include<cmath>
#define M(x) (x*x+x+41)
int dp[10100];
bool judge(int x)
{
if(x<=1) return 0;
for(int i=2;i*i<x+1;i++)
{
if(x%i==0) return 0;
}
return 1;
}
int main()
{
int a,b;
for(int i=0;i<=10010;i++)
dp[i]=judge(M(i));
while(~scanf("%d %d",&a,&b))
{
int cnt=0;
for(int i=a;i<=b;i++)
cnt+=dp[i];
double ans=cnt*1.0/(b-a+1)*100+1e-8; //记着后面要加精度,不然就 WA 了
printf("%.2lf\n",ans);
}
return 0;
}
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