длинная арифметика вычитание

#include <iostream>
#include <cmath>
using namespace std;

void minuss (int *a, int *b, int n, int m, int f)
{
  int l = f-1, s = n-1, c = m-1, times = s;

  int *result = new int[f];

  while(s > 0 && c > 0)
  {
    if (a[s] - b[c] < 0)
     {
       times = s-1;
       a[s] += 10;
       while (a[times] == 0)
        {
          a[times] += 9;
          times--;
        }

      a[times]--;
     }
     result[l] = a[s] - b[c];
     l--;
     s--;
     c--;
  }

  if (s >= 0 && c == 0)
  {
    if (a[s] - b[c] < 0)
     {
       times = s-1;
       a[s] += 10;
       while (a[times] == 0)
        {
          a[times] += 9;
          times--;
        }

      a[times]--;
     }
     result[l] = a[s] - b[c];
     l--;
     s--;
     c--;
  }

 while (s >= 0)
  {
     result[l] = a[s];
     l--;
     s--;
  }

int index = 0;

while (result[index] == 0)
  index++;

for (int i = index; i < f; i++)
   cout << result[i];
}

int main()
{
  int n, m;

  cin >> n >> m;

  int *a = new int[n];
  for ( int i = 0; i < n; i++)
   cin >> a[i];

  int *b = new int[m];
  for (int i =0; i < m; i++)
     cin >> b[i];

 minuss(a, b, n, m, n);
}