C++ infinite for loop i cant stop it

So i have this code to ask a user input which is numbers and put it to vector and i succesfully do it BUT when a user accidentally put a letter on it or any character it will go for a infinite for loop just a beginner :(

#include <iostream>
#include <vector>
using namespace std;
int main(){
    char letter{}; 
    int howmany {};
    vector <int> vector {};
    cout << "How many elements inside list? ";
    cin >> many;
    for (int i{1}; i <= howmany;i++){
        int arr {};
        cout << "Please enter number"<<endl;
        cin >> arr;
        vector.push_back(arr);