92分样例都过了，实在找不出原因，有没有大佬来指点一下

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#include <bits/stdc++.h>
using namespace std;
string a;
int sum, c;

int main() {
	cin >> c;
	cin >> a;
	for (int i = 0; i < a.size(); i++) {
		if (a[i] == 'V' && a[i + 1] == 'K') {
			sum += 1;
			a[i] = 'B';
			a[i + 1] == 'B';
		}
	}
	for (int i = 0; i < a.size(); i++) {
		if (a[i] == 'K' && a[i + 1] == 'K' || a[i] == 'V' && a[i + 1] == 'V') {
			sum++;
			cout << sum;
			return 0;
		}
	}
	cout << sum;
	return 0;
}