function main(input) {
  lines = input.split('\n')
  v = lines[0].split(' ').map((n) => parseInt(n));
  h = v[0];
  w = v[1];
  s = [];
  for (i = 1; i < h + 1; i++) {
    s.push(lines[i]);
  }
  dw = [];
  dh = [];
  for (i = 0; i < h; i++) {
    cw = [];
    count = 0;
    for (j = 0; j < w; j++) {
      if (s[i][j] == '#') {
        cw.push(0);
      } else if (j == 0 || s[i][j - 1] == '#') {
        count = 0;
        for (k = j; k < w; k++) {
          if (s[i][k] == '.') {
            count ++;
          } else {
            break;
          }
        }
        cw.push(count);
      } else {
        cw.push(count);
      }
    }
    dw.push(cw);
  }
  for (j = 0; j < w ; j++) {
   ch = [];
   count = 0;
   for (i = 0 ; i < h ; i++) {
     if (s[i][j] == '#') {
       ch.push(0);
     } else if (i == 0 || s[i - 1][j] == '#') {
       count = 0;
       for (k = i; k < h; k++) {
         if (s[k][j] == '.') {
           count += 1;
         } else {
           break;
         }
       }
       ch.push(count);
     } else {
       ch.push(count);
     }
   }
   dh.push(ch);
  }
  max = 0;
  for (i = 0; i< h; i++) {
    for (j = 0; j < w; j++) {
      sum = dw[i][j] + dh[j][i];
      if (max < sum) {
        max = sum;
      }
    }
  }
  console.log( max - 1);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'))
