[von JoSy]

Код:

program test;

const m = 3;
const n = 4;

var
    i, j, nmin, count, countpos: integer;
    a: array [1..m] of array [1..n] of integer;
    
begin

    for i:=1 to m do
        for j:=1 to n do
            read(a[i][j]);
            
    count := 0;
    countpos := m;
    nmin := 0;

    for j:=1 to n do begin
        count := 0;
        for i:=1 to m do begin
            if (a[i][j] > 0) and (countpos = m) then
                count := count+1
            else if a[i][j] > 0 then
                count := count+1;
        end;
        if count < countpos then begin
            countpos := count;
            nmin := j;
        end;
    end;

end.

P.S. Задачи очень легкие.