#include <bits/stdc++.h>
using namespace std;

#define scd(v) scanf("%d",&v)
#define scld(v) scanf("%ld",&v)
#define sclld(v) scanf("%lld",&v)
#define scs(v) scanf("%s",&v)
#define sclf(v) scanf("%lf",&v)

#define rep(i, j) for(int i = 0;i < j;i++)
#define all(v) v.begin(),v.end()
#define cnt(v,n) count(ALL(v),n)
#define sz(v) v.size()
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define inf int(1e9)
#define ll long long
#define pi 3.14159265358979

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<vi> vvi;
typedef vector<ll> vll;
typedef vector<vll> vvll;



void solve(){
    int a,b;
    string s;
    cin >> a >> b;
    cin >> s;
    for(int i = 0;s[i];i++){
        if(s[i] == 'x'){
            if(b > 0)b--;
        }else b++;
    }
    cout << b << endl;
}

int main(){
    ios_base::sync_with_stdio(false),cin.tie(0);
    int t=1;
    while(t--) solve();
    return 0;
}


#include <bits/stdc++.h>

using namespace std;

const int MX = 1e5 + 5;

int N, M;
long long int odd, even;
string s[MX];

int main(){
    cin.tie(nullptr), ios::sync_with_stdio(false);
    cin >> N >> M;
    for(int i = 0; i < N; i++) cin >> s[i];
    for(int i = 0; i < N; i++){
        int cnt = 0;
        for(char c : s[i]) if(c == '1') cnt++;
        if(cnt % 2 == 0) even++;
        else odd++;
    }
    cout << odd * even;
}
