#pragma GCC optimize("O3,unroll-loops")
#include<cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
int C,z=1e9,R, n, x[300], y[300], c[41][41];
int Check(int l, int u, int r, int d) {
memset(c,0,sizeof c);
for (int i = 0; i < n; ++i) {
++c[max(0, x[i]-u)][max(0, y[i]-l)];
--c[max(0, x[i]-u)][min(40,y[i]+r+1)];
--c[min(40,x[i]+d+1)][max(0, y[i]-l)];
++c[min(40,x[i]+d+1)][min(40,y[i]+r+1)];
}
for(int i=1;i<R;++i)c[i][0]+=c[i-1][0];
for(int j=1;j<C;++j)c[0][j]+=c[0][j-1];
for(int i=1;i<R;++i)for(int j=1;j<C;++j)c[i][j]+=c[i-1][j]+c[i][j-1]-c[i-1][j-1];
for(int i=0;i<R;++i)for(int j=0;j<C;++j)if(!c[i][j])return 0;
return 1;
}
int main() {
scanf("%d%d%d", &R, &C, &n);
for (int i = 0; i < n; ++i) scanf("%d%d", x + i, y + i), --x[i], --y[i];
for(int l=0;l<=40;++l)for(int r=0;r<=40-l;++r){
for(int u=0;u<=40;++u){
int lb=0,ub=39;
while(lb<=ub){
int md=lb+(ub-lb)/2;
if(Check(l,u,r,md))ub=md-1,z=min(z,l+u+r+md);
else lb=md+1;
}
}
}
printf("%d",z);
}
