请问这个问题应该如何做

#include<iostream>
using namespace std;
int a,b=0x3f3f3f3f,c=-1,sum,ans;
int main() {
    while(cin>>a&&a!=-1) {
        if(a>100||a<0) continue;
        b=min(b,a);
        c=max(c,a);
        sum+=a;
        ans++;
    }
    cout<<c<<" "<<b<<" "<<sum/ans;
    return 0;
}