#include<fstream>
#include<algorithm>
using namespace std;
ifstream fin("teren.in");
ofstream fout("teren.out");
char a[305][305];
int D[305][305], n, m, aria, x, sol, st, sum;
int main(){
    fin >> n >> m >> x;
    for( int i = 1; i <= n; i++ ){
        for( int j = 1; j <= m; j++ ){
            fin >> a[i][j];
        }
    }
    //D[i][j] = cati de unu sunt pe colona j pana la linia i inclusiv
    for( int i = 1; i <= n; i++ ){
        for( int j = 1; j <= m; j++ ){
            D[i][j] = D[i - 1][j] + (a[i][j] - '0');
        }
    }
    sol = 0;
    for( int i1 = 1; i1 <= n; i1++ ){
        for( int i2 = i1; i2 <= n; i2++ ){
            st = 1;
            sum = 0;
            for( int j = 1; j <= m; j++ ){
                sum += D[i2][j] - D[i1 - 1][j];
                while( sum > x && st <= j ){
                    sum -= ( D[i2][st] - D[i1 - 1][st] );
                    st++;
                }
                aria = (i2 - i1 + 1) * (j - st + 1);
                sol = max( sol, aria );
            }
            sol = max( sol, aria );
        }
    }
    fout << sol;
    return 0;
}