二分范围开到25才过了，银行利息这么高？？？

#include <iostream>
using namespace std;

int w0, w, m;

int check(double x) {
	double t1 = w0;
	for (int i = 1; i <= m; i++) {
		t1 *= (1 + x);
		t1 -= w;
	}
	if (t1 >= 0) {
		return 1;
	} else {
		return 0;
	}
}

int main() {
    cin >> w0 >> w >> m;
    double l = 0, r = 25, mid;
    while (r - l >= 0.0001) {
        mid = (l + r) / 2;
        if (check(mid)) {
			r = mid;
		} else {
        	l = mid;
		}
    }
    r *= 100;
    printf("%.1lf", r);
	return 0;
}