#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define ui unsigned int
#define ld long double
#define pl pair<long long int, long long int>
#define boost ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ff first
#define ss second
#define sz size()
#define all(x) x.begin(), x.end()
using namespace std;
const int maxn = 1e6 + 11;
const int inf = 1e17 + 1;
const int mod = 1e9 + 7;
// const int mod = 998244353;
const int dx[] = {-1, 0, 0, 1, -1, -1, 1, 1};
const int dy[] = {0, -1, 1 , 0, -1, 1, -1, 1};
const double eps = 1e-10;
int n, m;
void solve() {
cin >> n >> m;
if(n == 1 || m == 1) {
int mn = -1;
int cnt = 0;
for(int i = 1; i <= max(n, m); i++) {
int x;
cin >> x;
if(x == 1) {
cnt++;
}
else {
if(mn == -1 && cnt) {
mn = cnt;
cnt = 0;
continue;
}
mn = min(mn, cnt);
}
}
cout << mn;
}
}
signed main() {
// freopen("sum.in", "r", stdin);
// freopen("sum.out", "w", stdout);
boost;
int tt = 1;
// cin >> tt;
for(int i = 1; i <= tt; i++) {
// cout << "Case " << i << ":\n";
solve();
}
}
