//No.345 最小チワワ問題
#include<iostream>
#include<string>
using namespace std;
int findChiw(string S) {
	int cnt = 0;
	int chiw_num = 0;
	bool chiw_flag = false;
	string chiw = "chiwawa";
	for (int i = 0; i < S.length(); i++) {
		if (S[i] == chiw[cnt])
		{
			cnt++;
			chiw_flag = true;
		}
		if (chiw_flag)chiw_num++;
	}
	if (cnt != chiw.length())chiw_num = 0;
	if (chiw_num == 0)return -1;
	else return chiw_num-1;
}
int main()
{
	string S;
	cin >> S;
	cout << findChiw(S) << endl;
	return 0;
}