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

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int n, k, t;
	cin>>n>>k>>t;
	string a;
	cin>>a;
	vector <vector <int>> dp(3, vector <int> (n+7, -1));
	dp[0][0]=0;
	dp[1][0]=1;
	dp[2][0]=k;
	for (int i=0; i<n; i++)
	{
	    if (dp[1][i]==1) {
	        if (a[i]=='3') {
	            dp[0][i+1]=max(dp[0][i+1], dp[0][i]+1);
	            dp[1][i+1]=dp[1][i];
	            dp[2][i+1]=dp[2][i];
	        }
	        else if (a[i]=='2') {
	            if (dp[2][i]>0) {
	                dp[2][i+1]=dp[2][i]-1;
	                dp[0][i+1]=max(dp[0][i+1], dp[0][i]+1);
	                dp[1][i+1]=dp[1][i];
	            }
	            else {
	                dp[0][i+1]=dp[0][i];
	                dp[1][i+1]=dp[1][i];
	                dp[2][i+1]=dp[2][i];
	            }
	        }
	        else {
	            if (dp[2][i]>0) {
	                dp[2][i+1]=dp[2][i]-1;
	                dp[0][i+1]=max(dp[0][i+1], dp[0][i]+1);
	                dp[1][i+1]=dp[1][i];
	            }
	            else {
	                if (i<t || i>=n-t) {
	                    dp[0][i+1]=-1;
	                }
	                else {
	                    dp[0][i+1]=dp[0][i-t];
	                    dp[1][i+1]=2;
	                    dp[2][i+1]=dp[2][i-t];
	                }
	            }
	        }
	    }
	    else
	    {
	        if (a[i]=='3') {
	            dp[0][i+1]=dp[0][i];
	            dp[2][i+1]=dp[2][i];
	            dp[1][i+1]=dp[1][i];
	        }
	        else if (a[i]=='2') {
	            if (dp[2][i]>0) {
	                dp[2][i+1]=dp[2][i]-1;
	                dp[0][i+1]=max(dp[0][i+1], dp[0][i]+1);
	                dp[1][i+1]=dp[1][i];
	            }
	            else {
	                dp[0][i+1]=dp[0][i];
	                dp[1][i+1]=dp[1][i];
	                dp[2][i+1]=dp[2][i];
	            }
	        }
	        else {
	            if (dp[2][i]>0) {
	                dp[2][i+1]=dp[2][i]-1;
	                dp[0][i+1]=max(dp[0][i+1], dp[0][i]+1);
	                dp[1][i+1]=dp[1][i];
	            }
	            else {
	                dp[0][i+1]=dp[0][i];
	                dp[1][i+1]=dp[1][i];
	                dp[2][i+1]=dp[2][i];
	            }
	        }
	        if (i>=t && dp[i+1]==dp[i-t]) {
	            dp[1][i+1]=1;
	        }
	    }
	}
	cout<<dp[0][n];
}