应该是个很简单的题目 

#include<bits/stdc++.h>

using namespace std;

int main(){
    double a[7];
    for(int i=0;i<=6;i++){
        scanf("%lf",&a[i]);
        getchar();
        a[i] = a[i] /100.0;
    }

    int c ;
    double v;
    cin>>c>>v;
    if(v==1) v=0.01;
    else v =0.99;
    printf("%.2lf", a[c] * v*100);
    cout<<"%";
}