max of length index

#include<bits/stdc++.h>

using namespace std;

const int INF = 1e9 + 13;

int main(){
    ifstream in("input.txt");
    int Max_length = -INF;
    int answer = -1;
    int cur_index = 0;
    while(in.peek() != EOF)
    {
        cur_index++;
        string s;
        getline(in, s);
        if (int(s.length()) > Max_length)
        {
            Max_length = s.length();
            answer = cur_index;
        }
    }
    cout << answer;

}