bug of vector

#include <vector>int main(){//    freopen("in","r",stdin);    vector<int>  a;    a.clear();    a.push_back(1);    for(vector<int>::iterator it = a.begin();it!=a.end();++it){        if(*it<100) a.push_back(*it*2);    }}

 The code will make segmentation fault , I think It's the designer's fault