#include using namespace std; #define FOR(i,a,b) for(int i=(a);i<(b);i++) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() template inline bool chmax(A &a, B b) { if (a inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; } typedef unsigned long long ull; typedef long long ll; typedef pair pii; typedef pair pll; const ll INF = 1ll<<29; const ll MOD = 1000000007; const double EPS = 1e-10; int main() { int d; cin >> d; string s, tmp; cin >> s >> tmp; s += tmp; int dp[2][15] = {}; REP(i, s.size()) { if (s[i] == 'o') { chmax(dp[0][i + 1], dp[0][i] + 1); chmax(dp[1][i + 1], dp[1][i] + 1); } else { if (i + d <= s.size()) chmax(dp[1][i + d], dp[0][i] + d); } } int ans = 0; REP(i, 2) REP(j, s.size() + 1) chmax(ans, dp[i][j]); cout << ans << endl; return 0; }