class Solution {
public:
    int getUglyNumber(int n) {
        if(n <= 1) return n;
        vector<int> f(1,1);

        int i = 0,j = 0,k = 0;
        long long t = 0;

        while(--n){ //循环n-1次，n--为循环n次
            t = min(f[i] * 2,min(f[j] * 3,f[k] * 5));
            if(t == f[i] * 2) i++;
            if(t == f[j] * 3) j++;
            if(t == f[k] * 5) k++;
            f.push_back(t);
        }
        return f.back();    //返回f的最后一个元素
    }
};