In this Rabin Karp Algorithm implementation cp-algorithms Rabin-Karp Algorithm .

```
vector<int> occurences;
for (int i = 0; i + S - 1 < T; i++) {
long long cur_h = (h[i+S] + m - h[i]) % m;
if (cur_h == h_s * p_pow[i] % m)
occurences.push_back(i);
}
```

I’m not able to figure out why h_s is multiplied with prime number power. Like this is hash value of pattern for which we are searching then what is need to multiply it again here?