#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double dl;
typedef pair<dl,dl> pdi;
typedef pair<ll,ll> pii;
typedef pair<ll,pii> piii;

#define ff first
#define ss second
#define eb emplace_back
#define ep emplace
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define compress(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define IDX(v, x) lower_bound(all(v), x) - v.begin()
//cout<<fixed;
//cout.precision(12);

vector<ll> arr[1010101];
vector<ll> u[1010101];

ll n,m;
string s;
stack<pii> st;
ll inf=1e18;
ll calc(ll a,ll b,ll c){
    if(b==0) return inf;
    ll cnt=0;

    ll x=b;
    while(x<a+b){
        x*=2;
        cnt++;
    }
    if(a%b){
        x-=b-(a%b);
    }
    while(x<a+b+c){
        x*=2;
        cnt++;
    }
    //cout<<a<<' '<<b<<' '<<c<<' '<<cnt<<'\n';
    return cnt;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    cin>>n>>m;

    for(ll i=0;i<=n;i++){
        arr[i].resize(m+3);
    }

    ll ans=inf;

    for(ll i=1;i<=n;i++){
        cin>>s;
        //cout<<i<<' '<<s<<endl;
        for(ll j=1;j<=m;j++){
            if(s[j-1]=='1')
                arr[i][j]=arr[i-1][j]+1;
        }
        //cout<<i<<' '<<s<<endl;
        
        for(ll j=1;j<=m+1;j++){
            while(st.size()&&st.top().ff>=arr[i][j]){
                ll x=calc(i-st.top().ff,st.top().ff,n-i);
                ll y=calc(st.top().ss-1,j-st.top().ss,m-j+1);
                st.pop();
                ans=min(ans,x+y);
            }
            st.push({arr[i][j],j});
        }

        while(st.size()) st.pop();
    }

    cout<<ans;
}