#include<iostream>
using namespace std;
int main() {
int flag = 0,sum = 10000,cnt = 0;
while ((sum>=600&&flag == 0)||(sum>=0&&flag == 1)) {
if (flag == 0) {
sum -= 600;
flag = 1;
cnt++;
}
else{
sum += 300;
flag = 0;
cnt++;
}
}
cout << cnt * 60 + 60 * sum / 600;
return 0;
}