#include<iostream>
#include<queue>
using namespace std;
int main()
{
    int a, b, c;
    cin >> a >> b >> c;
    priority_queue<int>temp;
    temp.push(a);
    temp.push(b);
    temp.push(c);
    cout << temp.top();
}

不要亂吃毒...

int a,b,c;

cin>>a>>b>>c;

cout<<max(a,max(b,c))<<"\n";