function prefixStrings(a,b){
bol = true
options = []
s = ""
for (let i=0;i<a.length;i++){
let x= a[i]
s= s+x
options.push(s)
}
for (let j=0;j<b.length;j++) {
let y= b[j]
prefixfound = false
for (let i=0;i<options.length;i++) {
let x= options[i]
console.log(y.indexOf(x))
if(y.indexOf(x) == 0){
prefixfound = true
break
}
}
if(!prefixfound) return false
}
return bol
}