Metric-Converter

#include <iostream>
#include <iomanip>
#include <string>

using namespace std;

int main() {

    string metric_from;
    string metric_to;
    double metric_count = 0;
    double middle_value, total_value;

    cin >> metric_count;
    cin >> metric_from;
    cin >> metric_to;

    if  (metric_from == "mm") {
        middle_value = metric_count / 1000;
    }
    else if (metric_from == "cm") {
        middle_value = metric_count / 100;
    }
    else if (metric_from == "mi") {
        middle_value = metric_count / 0.000621371192;
    }
    else if (metric_from == "in") {
        middle_value = metric_count / 39.3700787;
    }
    else if (metric_from == "km") {
        middle_value = metric_count / 0.001;
    }
    else if (metric_from == "ft") {
        middle_value = metric_count / 3.2808399;
    }
    else if (metric_from == "yd") {
        middle_value = metric_count / 1.0936133;
    }
    else if (metric_from == "m") {
        middle_value = metric_count / 1;
    }

    //Middle to total_value

    if (metric_to == "mm") {
        total_value = middle_value * 1000;
    }
    else if (metric_to == "cm") {
        total_value = middle_value * 100;
    }
    else if (metric_to == "mi") {
        total_value = middle_value * 0.000621371192;
    }
    else if (metric_to == "in") {
        total_value = middle_value * 39.3700787;
    }
    else if (metric_to == "km") {
        total_value = middle_value * 0.001;
    }
    else if (metric_to == "ft") {
        total_value = middle_value * 3.2808399;
    }
    else if (metric_to == "yd") {
        total_value = middle_value * 1.0936133;
    }
    else if (metric_to == "m") {
        total_value = middle_value * 1;
    }

    cout << fixed << setprecision(8) << total_value << endl;

    return 0;
}