#include<bits/stdc++.h>
using namespace std;
int main(){
	double a,b;
	cin>>a>>b;
	cout<<fixed<<setprecision(3)<<1.0*b/a*100<<"%";
    return 0;
}

制作不易，点个赞再拿走嘛

#include<bits/stdc++.h> using namespace std; int main(){ double a,b; cin >> a >> b ; printf("%.3lf",b/a*100); cout<<"%"; return 0; }