#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main()
{
	string S;
	cin >> S;

	int ans = -1;
	int i = 0;
	int len = 200;
	char stat = 'c';
	int tmp;
	while( true ) {

		if( S[i] == '\0' )  {
			if( stat == 'c' ) {
				break;
			}
			i = tmp+1;
			stat = 'c';
			continue;
		}
		switch( stat ) {
		case 'c':
			if( S[i] == 'c' ) {
				stat = 'w';
				tmp = i;
			}
			i++;
			break;
		case 'w':
			if( S[i] == 'w' ) {
				stat = 'W';
			}
			i++;
			break;
		case 'W':
			if( S[i] == 'w' ) {
				len = min( len, i - tmp + 1 );
				i = tmp;
				stat = 'c';
			}
			i++;
		}

	}
	len = len==200 ? -1: len;
	cout << len << endl;

	return 0;
}