#include<cstdio>
//#include<windows.h>


int N,M,K,sR,R=-1,tR=1000000000;
int a[21][21];

int sum(int n0,int m0, int n, int m){
	int i,j,s=0;
	for(i=n0; i<=n; i++){
		for(j=m0; j<=m; j++){
			s+=a[i][j]; sR++;
		}
	}
	return s;
}

void Input(){
	FILE *In = fopen("minark.in","r");
	fscanf(In,"%i %i %i",&N,&M,&K);
	for(int i=1; i<=N; i++){
		for( int j=1; j<=M; j++){
			fscanf(In,"%i ", &a[i][j]);
		}
	}
	fclose(In);
}
void Output(){
	FILE *Out = fopen("minark.out","w");
	fprintf(Out,"%i",R);
	fclose(Out);
}

int main(){
	int i,j,ii,jj,tK;
	Input();
	for(i=1; i<=N; i++){
		for(j=1; j<=M; j++){
			for(ii=i; ii<=N; ii++){
				for(jj=j; jj<=M; jj++){
					sR=0;
					tK = sum(i,j,ii,jj);
					if(tK >= K){
						if(sR < tR){ R = sR; tR = sR;}
					}
				}
			}
		}
	}
	Output();
	return 0;
}<!-- 0.0407s -->