C++ :

#include<iostream>
#include<string>
#include<cstring>
using namespace std;
int s, t, w;
string num;
bool hasNext(int i, char c) {
	if (c>=('a'+t-1-(w-1-i))) return false;
	else return true;
}
void changeLater(int i) {
	for (i++; i < w; i++)
		num[i] = num[i-1]+1;
}
void next() {
	for (int i = w-1; i >= 0; i--) {
		if (hasNext(i, num[i])) {
			num[i] = num[i]+1;
			changeLater(i);
			break;
		}
	}
	cout << num << endl;
}
int main() {
	while (cin >> s >> t >> w) {
		cin >> num;
		for (int i = 0; i < 5; i++)
			next();
	}
	return 0;
}

Pascal :

var s,t,w,i,j,k:longint;str:string;
begin
  readln(s,t,w);
  readln(str);
  for i:=1 to 5 do
    begin
      j:=w;
      while (j>0)and(ord(str[j])-96=t-(w-j)) do dec(j);
      if j=0 then break;
      str[j]:=chr(ord(str[j])+1);
      for k:=j+1 to w do str[k]:=chr(ord(str[k-1])+1);
      writeln(str);
    end;
end.