how to call an if statement 64 times without 64 repeating statments?

function FindEmptySlot(){

if(items[1] == ""){
	openSlots = 64;
}
else if(items[2] == ""){
	openSlots = 63;
}

}

How can i repeat this function to get the empty item slot without literally typing it out for forever.

for(int i=1; i<=64; i++)
if(items == “”)
openSlots = 65 - i;