Uva 10200 - Prime Time

// Header file begin
#include<iostream>
#include<cstdio>
#include<cstring>
#include<map>
#include<string>
#include<vector>
#include<cmath>
#include<cctype>
#include<sstream>
#include<set>
#include<list>
#include<stack>
#include<utility>
#include<queue>
#include<algorithm>
#include<cstdlib>
// End
//..........
// Macro
#define sf scanf
#define pf printf
#define lp1(i,n) for(i=0;i<n;i++)
#define lp2(i,n) for(i=1;i<=n;i++)
#define mset(c,v) memset(c,v,sizeof(c))
#define cp(a) cout<<" "<<a<<" "
#define nl puts("")
#define sq(x) ((x)*(x))
#define all(x) x.begin(),x.end()
#define reall(x) x.rbegin(),x.rend()
#define s_wap(x,y) x^=y;y^=x;x^=y;
#define sz size()
#define gc getchar()
#define pb push_back
#define freader freopen("input.txt","r",stdin)
// End.........

// Size
#define mx7 20000100
#define mx6 1500000
#define mx5 100005
#define mx4 1000100
#define inf 1<<30                                           //infinity value
#define eps 1e-9
#define mx (65540)
#define mod 1000000007
#define pi acos(-1.0)

// Macros for Graph

#define white 1
#define gray 2
#define black 3
#define nil 0

using namespace std;
/***************/

// typedef

typedef long long LL;
typedef long L;
typedef unsigned long long ull;
typedef unsigned long ul;
typedef unsigned int ui;
typedef pair<int, int> pii;
typedef vector<int>vi;
typedef vector<long long> vll;
typedef vector<long>vl;
typedef vector<char>vch;
typedef vector<string>vs;
typedef map<int,int>mpii;
typedef map<int,bool>mpbi;
typedef map<long,bool>mpbl;
typedef map<long long,bool>mpbll;
typedef map<char,int>mpci;
typedef map<char,bool>mpbc;
typedef map<string,int>mpsi;
typedef map<long long,long long>mpll;

// template

template<class T> T gcd(T a, T b ) {return b!=0?gcd<T>(b,a%b):a;}
template<class T> T large(T a, T b ) {return a>b?a:b;}
template<class T> T small(T a, T b ) {return a<b?a:b;}
template<class T> T diffrnce(T a, T b) {return a-b<0?b-a:a-b;}

int prime[(mx7>>6)+1],prm[(mx7>>1)+9],plen=0;

// macros for seieve

#define setbit(n) (prime[n>>6] |= (1 << ((n>>1)&31)))
#define checkbit(n) (prime[n>>6] & (1 << ((n>>1)&31)))

void sieve()
{
    int i,j;
    for(i=3;i*i<=mx7;i+=2)
    {
        if(!checkbit(i))
        {
            for(j=i*i;j<=mx7;j+=i+i)
            {
                setbit(j);
            }
        }
    }
    prm[plen++]=2;
    for(i=3;i<=mx7;i+=2)
    {
        if(!checkbit(i))
        {
            prm[plen++]=i;
        }
    }
    //lp1(i,100)cp(prm[i]);
}

bool isPrime(LL n)
{
    int i;
    for(i=0;i<plen and sq(prm[i])<=n;i++)
    {
        if(!(n%prm[i]))
        {
            return false;
        }
    }

    return true;
}

bool flag[mx4+9];

void ptime()
{
    mset(flag,false);
    int i;
    for(i=0;i<10009;i++)
    {
        LL r=sq(i)+i+41;

        if(isPrime(r))
        {
            flag[i]=true;
        }
    }
}

int main()
{
    sieve();
    ptime();
    LL x,y;
    while(~sf("%lld %lld",&x,&y))
    {
        if(y==0)
        {
            pf("100.00\n");
            continue;
        }

        if(x>y)
        {
            s_wap(x,y);
        }

        LL cnt=0,d=(y-x)+1.00;

        for(LL i=x;i<=y;i++)
        {
            if(flag[i])
            {
                cnt+=1;
            }
        }

        //cp(cnt);

//        double ans=(double)cnt*100.00; //cp(ans);
//        ans=(double)ans/d+1.0e-7;
        pf("%.2lf\n",(cnt * 100.0) / (double)d + 1e-9);
    }

    return 0;
}