Envío 6400

Código

import java.util.*;
public class Main {

    public static void main(String[] args) throws java.lang.Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();  
		
		int [][] m = new int [n][n];
		for(int i =0; i<n; i++){
		  for(int j =0; j<n; j++){
		  	m[i][j]= sc.nextInt();
		  }
		}
		

       System.out.println(isMagicSquare(m));
}

		public static String isMagicSquare(int [][] m){
		
		int lastRow=0;
		int row=0;
		int col=0;
		int lastColumn=0;
		int upperDiag = 0;
		int lowerDiag = 0;
			for(int i =0, z=m.length-1; i<m.length; i++,z--){
				if((row!=lastRow && i>1) || (col!=lastColumn && i>1)) return "no";
			     lastRow = row;
			     row=0;
			     lastColumn = col;
			     col=0;
			     upperDiag+=m[i][i];
			     lowerDiag += m[i][z];
				   for(int j =0; j<m.length; j++){
			       row += m[i][j];
			       col += m[j][i];
		    }
		}
		

		return col==row && col==upperDiag && col==lowerDiag ? "yes": "no";
		}
  
}