Erasing elements from a vector

The following code initializes an STL vector of integers to $(2,1)$ then iterates to erase all elements with value 1. The code compiles but on running it we get a segmentation fault abort. Find and fix the bug.

// this program is buggy!
#include<vector>
int main(int argc, char** argv) {
  using namespace std;
  int ret = 0;
  vector<int> theVector;
  theVector.push_back(2);
  theVector.push_back(1);
  vector<int>::iterator vi;
  for(vi = theVector.begin(); vi != theVector.end(); vi++) {
    if (*vi == 1) {
      theVector.erase(vi);
    }
  }
  return ret;
}