Функция

#include <iostream>
#include <cmath>
#include <string>
using namespace std;
double circle (int r) {
    const double  p = 3.1415926535897932384626433832795;
    double s;
    s = p * r * r;
    return s;
}
double rectangle (int a, int b) {
    int s;
    s = a * b;
    return s;
}
double triangle (int x, int y, int z) {
    double s, h;
    h = (x + y + z) / 2;
    s = sqrt(h * (h - x) * (h - y) * (h - z));
    return s;
}
int main () {
    cout << "What is your figure? ";
    string g;
    double a, b, r, x, y, z, k;
    cin >> g;

    if(g == "Circle" || g == "circle" || g == "rectangle" || g == "Rectangle" || g == "triangle" || g == "Triangel") {
    cout << "Enter your data ";
    if (g == "Circle" || g == "circle") {

        cin >> r;
        k = circle(r);
    }
    else if (g == "Rectangle" || g == "rectangle") {
        cin >> a >> b;
        k = rectangle(a, b);

    }


    else {
        cin >> x >> y >> z;
        k = triangle(x, y, z);
    }
    cout << k;
    } else {
        cout << "WRONG";
    }

    return 0;
}