#include<iostream>
#include<cmath>
#include<iomanip>
#include<cstdio>
#include<algorithm>
using namespace std;
int main()
{
    long long i,j,k,a,b,m,n,tmp,s,t,best;
    double distance;
    long special[1005][4];  //special[i][0]表示第i条斜边左下角顶点x坐标，special[i][1]表示第i条斜边左下角顶点y坐标
    long x,y;

    {cin>>n>>m;  //读入 
    cin>>k;
    for (i=1;i<=k;++i) //读入一叠叠的坐标
     cin>>special[i][0]>>special[i][1];
    }

    for (i=1;i<=k;++i)  //冒泡排序，准则：先x后y升序排列，使需要查找时向左查找 ★现在做的是x升序排序★纵坐标不用排★
      { for (j=i+1;j<=k;++j)
       { if (special[i][0]>special[j][0])
         { for (s=0;s<=3;++s)  //整个点的所有内容转移，懒得打4遍
           {tmp=special[i][s];special[i][s]=special[j][s];special[j][s]=tmp;}         
          }
        }
       }

      
      for (i=1;i<=k;++i) special[i][2]=0;  //初始化special[i,2]值,使自己算一条 
      
      
      for (i=1;i<=k;++i)
      { for (j=1;j<=i;++j)
        { if ((special[i][0]>special[j][0])and(special[i][1]>special[j][1]))
           { if (special[j][2]+1>special[i][2]) special[i][2]=special[j][2]+1; }
         } 
       }

      distance=100*m+100*n;
      best=0;
      for (i=1;i<=k;++i) 
      {if (special[i][2]>best) best=special[i][2];}

      best=best+1;

      distance=distance-200*best+best*sqrt(2)*100;

      
      cout<<int(distance+0.5)<<endl;
     return 0;      
}