加总价的时候单价会改变
加数量单价不会改变
特判一次 贪心取就可以了
#include<bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
int main () {
double x, y;
while (scanf("%lf%lf", &x, &y) == 2) {
if (x > y) {
printf("-1\n");
continue;
}
double k = (y+1-eps) / x;
int cnt = (int)x - 1;
double tmp = 1;
for (int i = 1; i <= (int)x; i++) {
double t = i * k;
int u = (int)(t-tmp);
tmp += u;
tmp = tmp * (i+1) / i;
cnt += u;
}
printf("%d\n", cnt);
}
return 0;
}