uva10200

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/* ***********************************************Author       : rycCreated Time : 2016-08-14 SundayFile Name    : E:\acm\大三暑假\uva10200.cppLanguage     : c++Copyright 2016 ryc All Rights Reserved************************************************ */#include<iostream>#include<cstdio>#include<cstdlib>#include<algorithm>#include<cstring>#include<queue>#include<list>#include<stack>#include<vector>#include<map>using namespace std;typedef long long LL;typedef pair<int,int>pii;const int maxn=10010;double ans[maxn];bool judge(LL n){    for(LL i=2;i*i<=n;++i){        if(n%i==0)return false;    }    return true;}void Count(){   ans[0]=1;    for(LL i=1;i<maxn;++i){        if(judge(i*i+i+41)){            ans[i]=ans[i-1]+1;        }        else {            ans[i]=ans[i-1];        }    }}int main(){    Count();    int a,b;    while(scanf("%d%d",&a,&b)!=EOF){        if(a==0){            printf("%.2lf\n",ans[b]*1.0/(b+1)*100.0+1e-8);        }        else {            printf("%.2lf\n",(double)(1.0*(ans[b]-ans[a-1])*1.0/(b-a+1))*100.0+1e-8);        }    }    return 0;}

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