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if-else判断嵌套，头文件只需iostream就行了哦！
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#include<iostream>
using namespace std;
int main(){
    int n,m,x,a=17,b,c;
    cin>>n>>m>>x;
    if(x-15<=0)cout<<"late";
    else{
        x-=15;
        b=5+n;
        c=10+m;
        if(a<=b){
            if(a<=c){
                if(a<=x)cout<<"on time";
                else cout<<"late";
            }
            else{
                if(c<=x)cout<<"on time";
                else cout<<"late";
            }
        }
        else{
            if(b<=c){
                if(b<=x)cout<<"on time";
                else cout<<"late";
            }
            else{
                if(c<=x)cout<<"on time";
                else cout<<"late";
            }
        }
    }
    return 0;
}