n=int(input())
e=0
if(n>=90 or n==100):
    if(n>100):
        print("error")
        e+=1
        if(e==0):
            print("Excellent")
    if(n>=90 and n<=100):      
        print("Excellent")
elif(n>=70 and n<=80):
    print("good")
elif(n>=0 and n<=69):    
    print("normal")

简单，3个数比大小代码改一改就行了

#include <cstdio>
using namespace std;
int main()
{
    int a;
    cin>>a;
    if(a>=90&&a<=100)
    {
        cout<<"Excellent";
    
    }
    else if(a<90&&a>=70)
    {
        cout<<"good";
    }
    else if(a<70&&a>=0)
    {
        cout<<"normal";
    }
  else{
      cout<<"error";
  }
    return 0;
}