void shortpath_FLOYD(int cost[][M],int path[][M],int length[][M],int n)
{  int i,j,k,wm;
   for(i=0;i<n;i++)
     for(j=0;j<n;j++)
     {  length[i][j]=cost[i][j];
        if(i==j) path[i][j]=0;
        else if(length[i][j]<MAX)
            path[i][j]=i+1;
        else  path[i][j]=0;
     }
   for(k=0;k<n;k++)
     for(i=0;i<n;i++)
       for(j=0;j<n;j++)
         if(length[i][k]+length[k][j]<length[i][j])
         {  length[i][j]=length[i][k]+length[k][j];
            path[i][j]=path[k][j];
         }
}