All of them. Technically you only need to actually climb one of them and that's the most challenging although it wasn't because I'm a competent rock climber. That would be the inaccessible pinnacle on sgurr dearg.
We went to Chamonix for two weeks in July staying with friends and did some alpine routes leading up to the Cassin route on the Walker Spur of the north face of the Grandes Jorasses. That's the hardest route I've done 1200m on mixed quality rock. Three days total with two stops one in a refuge one a bivouac on the descent into Italy.