#include<bits/stdc++.h>
using namespace std;
char a[100][100];
int b[105][105];

int main(){
    int n,m,l,d,min1=9999999;
    cin>>n>>m>>l;
    for(int i=1;i<=n;i++){
		cin>>a[i];
		for(int j=1;j<=m;j++){
			if(a[i][j-1]!='0'){
				b[i][j]++;
			}
			b[i][j]+=b[i][j-1]+b[i-1][j]-b[i-1][j-1]; 
		}
		
		
    }
    for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			for(int i1=i;i1<=n+1;i1++){
				for(int j1=j;j1<=m+1;j1++){
					
					d=b[i1][j1]-b[i-1][j1]-b[i1][j-1]+b[i-1][j-1];;
					
					if(d>=l&&((i1-i+1)*(j1-j+1))<min1){
						
						min1=((i1-i+1)*(j1-j+1));
					}
				}
			}
		}
	}
	if(min1==9999999){
		cout<<0;
		return 0;
	}
	cout<<min1;
}