Вывести номер элемента вектора по его значению

#include <iostream>
#include <vector>
using namespace std;
int main ()
{
    int contra;
    string contra = " ";
    vector<string> words(11);
    words[0] = "zero";
    words[1] = "one";
    words[2] = "two";
    words[3] = "three";
    words[4] = "four";
    words[5] = "five";
    words[6] = "six";
    words[7] = "seven";
    words[8] = "eight";
    words[9] = "nine";
    words[10] = "ten";
    cin >> contra;
    cout << words.size(contra);

#include <iostream>
#include <vector>
#include <string>
 
using namespace std;
 
int main()
{
    vector<string> words(11);
    words[0] = "zero";
    words[1] = "one";
    words[2] = "two";
    words[3] = "three";
    words[4] = "four";
    words[5] = "five";
    words[6] = "six";
    words[7] = "seven";
    words[8] = "eight";
    words[9] = "nine";
    words[10] = "ten";
 
    string contra;
    cin >> contra;
 
    int result = -1;
    for (int i = 0; i < 11; i++)
    {
        if (words[i] == contra)
        {
            result = i;
            break;
        }
    }
 
    if (result != -1) std::cout << result;
 
    return 0;
}

vector<string> words = {"zero", "one", "two", ...};