#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define fi first
#define se second
#define pb push_back

int main(){
  int n,m;
  cin>>n>>m;
  if(n==1&&m==1){
    printf("0\n");
    printf("1 1\n");
    return 0;
  }
  else if(n%2==0&&m%2==0){
    printf("%d\n",n*m-1);
    int nowi=1,nowj=1;
    int op=1;
    int count=0;
    while(count!=n*m){
      if(op==1){
        if(nowj==m-1){
          op=2;
          continue;
        }
        else{
          printf("%d %d\n",nowi,nowj);
          printf("%d %d\n",nowi+1,nowj+1);
          printf("%d %d\n",nowi+1,nowj);
          printf("%d %d\n",nowi,nowj+1);
          count+=4;
          nowj+=2;
        }
      }
      else if(op==2){
        printf("%d %d\n",nowi,nowj);
        printf("%d %d\n",nowi+1,nowj+1);
        printf("%d %d\n",nowi,nowj+1);
        printf("%d %d\n",nowi+1,nowj);
        nowi+=2;
        op=3;
        count+=4;
        continue;
      }
      else if(op==3){
        printf("%d %d\n",nowi,nowj);
        printf("%d %d\n",nowi+1,nowj+1);
        printf("%d %d\n",nowi,nowj+1);
        printf("%d %d\n",nowi+1,nowj);
        nowi+=1;
        nowj-=1;
        op=4;
        count+=4;
        continue;
      }
      else if(op==4){
        if(nowj==1){
          op=1;
          continue;
        }
        else{
          printf("%d %d\n",nowi,nowj);
          printf("%d %d\n",nowi-1,nowj-1);
          printf("%d %d\n",nowi-1,nowj);
          printf("%d %d\n",nowi,nowj-1);
          count+=4;
          nowj-=2;
        }
      }
    }
  }
  else{
    printf("-1");
  }
}