/in/foo.cc:1:26: warning: extra tokens at end of #include directive
 #include <bits/stdc++.h> using namespace std; int n, Mx[10000010]; long long ans; int main() {    ios::sync_with_stdio(false);    cin.tie(NULL);    cin >> n;    for (int x, y, i = 1; i <= n; i++) {        cin >> x >> y;        x /= 2, y /= 2;        Mx[x] = max(Mx[x], y);    }    for (int h = 0, i = 10000000; i >= 1; i--) {        h = max(h, Mx[i]);        ans += h;    }    cout << ans * 4 << '\n';    return 0; }
                          ^~~~~
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status