for(int i=0; i<2; i++)for(int j=0; j<MAXN; j++)dp[i][j] = INF;

dp[1%2][1] = 0.0;

//dp[1][1] = 0.0;

for(int i=1; i<=N+1; i++){

for(int j=1; j<=M+1; j++){

if(dp[i%2][j]==INF)continue;

//if(dp[i][j]==INF)continue;

for(int k=0; k<cnt; k++){

if(diag[k][0]==i&&diag[k][1]==j){

dp[(i+1)%2][(j+1)] = min(dp[(i+1)%2][(j+1)], (dp[i%2][j]+141.421));

//dp[(i+1)][(j+1)] = min(dp[(i+1)][(j+1)], (dp[i][j]+141.421));

//cout<<"ok now i,j are "<<i<<" "<<j<<" and "<<dp[i%2][j]<<endl;

//cout<<"en-> min is "<<min(dp[(i+1)%2][j+1], dp[i%2][j]+141.421)<<endl;

//cout<<"first is "<<dp[(i+1)%2][j+1]<<" second is "<<dp[i%2][j]+141.421<<endl;

//cout<<"next "<<dp[(i+1)%2][j+1]<<endl;

//cout<<"diag "<<i<<" "<<j<<endl;

break;

}

}

dp[(i+1)%2][j] = min(dp[(i+1)%2][j],dp[i%2][j]+100);

//dp[(i+1)][j] = min(dp[(i+1)][j],dp[i][j]+100);

dp[i%2][(j+1)] = min(dp[i%2][(j+1)],dp[i%2][j]+100);

//dp[i][(j+1)] = min(dp[i][(j+1)],dp[i][j]+100);

//cout<<"at "<<i<<" "<<j<<" "<<dp[i%2][j]<<endl;

}

if(i==N+1)break;

for(int j=0; j<MAXN; j++)dp[i%2][j] = INF;

}

//cout<<M+1<<" "<<N+1<<endl;

//cout<<int((dp[(N+1)%2][(M+1)]+0.5))<<endl;

cout<<int((dp[(N+1)%2][(M+1)]+0.5))<<endl;

cin>>N>>M;

cin>>cnt;

for(int i=0; i<cnt; i++){

cin>>diag[i][0]>>diag[i][1];

}

work();

return 0;