#include<bits/stdc++.h>
using namespace std;
#define ll int
#define MAXN 10000010
inline ll read(){
	ll x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
ll dp[MAXN][5];
ll k;
//char c[MAXN];
int main(){
	freopen("changgao_modulo.in","r",stdin);
	freopen("changgao_modulo.out","w",stdout);
	k=read();
	for(int i=0;i<=4;i++)dp[0][i]=i*k;
	string s;
	cin>>s;
	ll len=s.length();
	s="0"+s;
	for(int i=1;i<=len;i++){
		ll a=(s[i]=='0'?0:k-(s[i]-'0')),b=(s[i-1]=='0'?0:k-(s[i-1]-'0'));
		for(int j=0;j<=4;j++){
			dp[i][j]=1e9;
			for(int u=0;u<=4;u++){
				ll _a=a+j*k,_b=b+u*k;
				dp[i][j]=min(dp[i][j],dp[i-1][u]+max(0,_a-_b));
			}
		}
//		cout<<i<<" "<<dp[i][0]<<" "<<dp[i][1]<<endl;
//		if(min(dp[i][0],dp[i][1])<=4999864)cout<<a;
	}
//	cout<<endl;
//	cout<<min(dp[len][1],dp[len][0]);
	ll ans=1e9;
	for(int i=0;i<=4;i++){
		ans=min(ans,dp[len][i]);
	}
	cout<<ans;
	return 0;
}