if (bars < distance (grid.begin(), grid.end()) - 1) {
/* grid contains beats and bars */
beats = distance (grid.begin(), grid.end()) - bars;
} else {
/* grid contains only bars */
beats = distance (grid.begin(), grid.end());
if (bars < distance (grid.begin(), grid.end()) - 1) {
/* grid contains beats and bars */
beats = distance (grid.begin(), grid.end()) - bars;
} else {
/* grid contains only bars */
beats = distance (grid.begin(), grid.end());