Найти сумму всех элементов массива

program Project2;
uses
 crt;
type vector = array[1..1000] of integer;
matrix = array[1..100]of vector;
var 
    a:matrix;
    i,n,m,sum:integer;
procedure ShowMatrix(a:matrix;n,m:integer);
var i:integer;
begin
    for i:=1 to n do 
  begin
  for j:=1 to m do 
    write(a[i,j],' ');
    writeln;
 end;
 writeln;
end;
procedure InitArray(var a:matrix;n,m:integer);
var i,j:integer;
begin
for i:=1 to n do 
  begin
  for j:=1 to m do 
    a[i,j] := random(100);  
 end;
end;
function SummaElementov(var a:matrix;n,m:integer):integer;
var sum:integer;
begin
    sum := 0;
    for i:=1 to n do 
        for i:=1 to m do 
        begin
            sum := sum + a[i,j];
        end;
    SummaElementov := sum;
end;
 
begin
 write('n=');readln(n);
 write('m=');readln(m);
 InitMatrix(a,n,m);
 ShowMatrix(a,n,m);
sum :=SummaElementov(a,n,m);
writeln('Summa elementov matritsi S= ',sum);
  readln;
  { TODO -oUser -cConsole Main : Insert code here }
end.

procedure InitArray(var a:matrix;n,m:integer);
var i,j:integer;
begin
for i:=1 to n do 
  begin
  for j:=1 to m do 
    a[i,j] := random(100) - 50;{vot zdesi zapolniaetsia matritsa}   
 end;
end;