#include<bits/stdc++.h>
#define endl '\n'
#define int long long
using namespace std;
int n,m,k,mn=10000000;
int s[110][110];
int c[110][110]; 
bool f=1;
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m>>k;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			scanf("%1d",&s[i][j]);
			c[i][j]=c[i-1][j]+c[i][j-1]-c[i-1][j-1]+s[i][j];
		}
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			for(int v=i;v<=n;v++){
				for(int g=j;g<=m;g++){
					if(c[v][g]+c[i-1][j-1]-c[i-1][g]-c[v][j-1]>=k){
						mn=min(mn,(v-i+1)*(g-j+1));
						f=0;
					}
				}
			}
		}
	}
	if(f){
		cout<<0;
		return 0;
	}else{
		cout<<mn;
	}
	return 0;
}
//0000000
//0000000
//0001000
//0000000
//0000010
//0000000
//0000000