#include <algorithm>
#include <cstdio>
#include <vector>
const size_t kMaxNumberOfSubmit = 100;
struct SubmitInfo {
int number_of_submit;
int time_of_submit;
int score_of_submit;
bool operator <(const SubmitInfo& a) const {
if (this->score_of_submit > a.score_of_submit) {
return true;
}
else if (this->score_of_submit == a.score_of_submit) {
if (this->number_of_submit < a.number_of_submit) {
return true;
}
}
return false;
}
};
int main() {
int number_of_submit = 0;
std::vector<SubmitInfo> bundle_of_submit_info;
scanf(" %d", &number_of_submit);
for (int i = 0; i < number_of_submit; ++i) {
SubmitInfo submit_info;
submit_info.number_of_submit = i + 1;
scanf(" %d %d", &submit_info.time_of_submit, &submit_info.score_of_submit);
bundle_of_submit_info.push_back(submit_info);
}
std::sort(bundle_of_submit_info.begin(), bundle_of_submit_info.end());
const int f = bundle_of_submit_info.at(0).number_of_submit;
if (bundle_of_submit_info.at(0).score_of_submit == 0) {
printf("%d\n", 0);
}
else {
printf("%d\n", bundle_of_submit_info.at(0).time_of_submit + (f - 1) * 20);
}
}
