using System;               

public class Program{

public static void Main(){

int n=5;//esta es tu n

int RandomSeed=0;//Valor Final es 31

int[,] m=new int[n,n];

var r=new Random(RandomSeed);

for(int x=0;x<n;x++){

for(int y=0;y<n;y++){

var rr=r.Next(0,9);

m[x,y]=rr;

}       

}

var xx=0;

var cc=0;

for(int y=0;y<n;y++){

var n1=m[xx,y];

cc+=n1;

xx+=1;

}

Console.WriteLine(cc);

}

}