#include <bits/stdc++.h>

 #define LL long long

 #define lowbit(x) x&(-x)

 #define inf 0x3f3f3f3f

 using namespace std;

 inline int ra()

 {

     int x=,f=; char ch=getchar();

     while (ch<'' || ch>'') {if (ch=='-') f=-; ch=getchar();}

     while (ch>='' && ch<='') {x=x*+ch-''; ch=getchar();}

     return x*f;

 }

 double dp[][];

 int n,m,t1,t2;

 bool r[],c[];

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

 {

     n=ra(); m=ra();

     t1=t2=n;

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

     {

         int x=ra(),y=ra();

         if (!r[x]) r[x]=,t1--;

         if (!c[y]) c[y]=,t2--;

     }

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

     {

         dp[i][]=dp[i-][]+(double)n/i;

         dp[][i]=dp[][i-]+(double)n/i;

     }

     for (int i=; i<=t1; i++)

         for (int j=; j<=t2; j++)

         {

             dp[i][j]=n*n;

             dp[i][j]+=i*j*dp[i-][j-];

             dp[i][j]+=i*(n-j)*dp[i-][j];

             dp[i][j]+=j*(n-i)*dp[i][j-];

             dp[i][j]/=(n*n-(n-i)*(n-j));

         }

     printf("%.10lf\n",dp[t1][t2]);

     return ;

 }