function solution(topping) {
const a = new Set();
const b = {};
let ans = 0;
let check = 0;
for(const t of topping) {
if(b[t]) b[t]++;
else {
b[t] = 1;
check++;
}
}
for(const t of topping) {
a.add(t);
b[t]--;
if(!b[t]) check--;
if(a.size === check) ans++;
}
return ans;
}