#include<stdio.h>
int main()
{
	int m,n,i,j;
	float a[99][99],average,sum=0;
	scanf("%d\n",&m);
	scanf("%d\n",&n);
	for( i=1;i<=m;i++)
	{
		for( j=1;j<=n;j++)
		scanf("%f",&a[i][j]);
		if(j==n)
		printf("\n");
	} 
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=m;j++)
		sum+=a[i][j];
	}
	average=sum/(n*m);
	printf("%f",average);
	return 0;
}