#define TIME 5

using namespace std;

//============================

int main(void)

{

int s, t, w;

// du qu shu ru.//

cin>> s>> t>> w;

char arr[w+1];

cin>> arr;

// kai shi shu chu.//

int i, j, k;

for (i = 0; i < TIME; i++) {

for (j = w-1; j >=0; j--) {

if (arr[j]+1 <= ('a'+(t-(w-j)))) {

arr[j] += 1;

for (k = j+1; k < w; k++)

arr[k] = arr[j] + (k-j);

cout<< arr<< endl;

break;

}

}

}

return 0;

}