import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		String S = sc.next();
		
		String comp = S;
		
		int flag = 0;
		
		for(int i = 0; i < S.length(); i++) {
			if(S.substring(i, i + 1).equals("c")) {
				S = S.substring(i);
				comp = S;
				//System.out.println(S);
				S = S.substring(S.indexOf("w") + 1);
				//System.out.println(S);
				if(S.indexOf("w") == -1) {
					flag = 1;
					break;
				} else {
					S = S.substring(S.indexOf("w") + 1);
					//System.out.println(S);	
				}
			}
		}
		
		if(flag == 0) {
			System.out.println(comp.length() - S.length());
		} else {
			System.out.println(-1);	
		}
	}
}