uva11429(生成随机数 期望)

//

//  main.cpp

//  uva11429

//

//  Created by New_Life on 16/8/4.

//  Copyright © 2016年 chenhuan001. All rights reserved.

//

#include <iostream>

#include <math.h>

#include <string>

#include <stdio.h>

#include <algorithm>

using namespace std;

#define N 1010

#define eps 1e-12

long double g[N];

int main(int argc, const char * argv[]) {

    int r,n;

    while(scanf("%d%d",&r,&n) && !(r==&&n==))

    {

        for(int i=;i<n;i++)

        {

            int a,b;

            scanf("%d%d",&a,&b);

            g[i] = (long double)a/b;

        }

        long double sum = 1.0;

        long double dr = ;

        long double up = ;

        long double ans = 1.0;

        long double preans;

        do

        {

            long double tmp=;

            dr *= r;

            up *= r;

            for(int i=;i<n;i++)

            {

                long long tmpi = (long long)(g[i]*dr+eps);

                g[i] -= (long double)tmpi/dr;

                up += tmpi;

            }

            preans = ans;

            ans += (dr-up)/dr;

            //ans += sum;

        }while(ans-preans>1e-);

        printf("%.6Lf\n",ans);

    }

    return ;

}

/*

 100 3

 1 3 1 3 1 3

 2 4

 1 4 1 4 1 4 1 4

 2 3

 1 3 1 3 1 3

 10 2

 1 2 1 2

 */

//用long double 才过的...