int maxSongs(vector <int> duration, vector <int> tone, int T) {
IIVec v;
int N = (int)tone.size();
int i, j, k;
for (i = 0; i < N; ++i) {
v.push_back(II(tone[i], duration[i]));
}
sort(v.begin(), v.end());
#define INF 0x3f3f3f3f
int dp[64][64] = {};
memset(dp, 0x3f, sizeof(dp));
for (i = 0; i < N; ++i) {
for (j = 0; j < i; ++j) {
for (k = 1; k <= i; ++k) {
dp[i][k+1] = min(dp[i][k+1], dp[j][k] + v[i].first-v[j].first + v[i].second);
}
}
dp[i][1] = v[i].second;
}
int ans = 0;
for (k = 1; k <= N; ++k) {
for (i = 0; i < N; ++i) {
if (dp[i][k] <= T) {
ans = k;
}
}
}
return ans;
}
int maxSongs(vector <int> duration, vector <int> tone, int T) {
int ans = 0;
IIVec v;
for (int i = 0; i < (int)tone.size(); ++i) {
v.push_back(II(tone[i], duration[i]));
}
sort(v.begin(), v.end());
int dp[64][64];
memset(dp, 0x3f, sizeof(dp));
for (int i = 0; i < (int)v.size(); ++i) {
for (int j = 0; j < i; ++j) {
for (int k = 1; k <= i; ++k) {
dp[i][k + 1] = min(dp[i][k + 1], dp[j][k] + abs(v[i].first - v[j].first) + v[i].second);
if (dp[i][k + 1] <= T) {
ans = max(ans, k + 1);
}
}
}
dp[i][1] = v[i].second;
if (v[i].second <= T) {
ans = max(ans, 1);
}
}
return ans;
}
double maxExpectation(int M, vector <int> day, vector <int> win, vector <int> gain) {
Max = M;
IIVec Days;
int i;
for (i = 0; i < (int)day.size(); ++i) {
if (win[i] > 0 && gain[i] > 0) {
Days.push_back(II(day[i], i));
}
}
sort(Days.begin(), Days.end());
_day.clear();
_win.clear();
_gain.clear();
memset(memo, 0, sizeof(memo));
for (i = 0; i < (int)Days.size(); ++i) {
_day.push_back(Days[i].first);
_win.push_back(win[Days[i].second] * 0.01);
_gain.push_back(gain[Days[i].second]);
}
if (Days.size() <= 0 || M <= _day[0]) {
return M;
}
return rec(0, M - _day[0]);
}
vector <int> minimalDifference(vector <int> h) {
int N = (int)h.size();
IIVec v;
for (int i = 0; i < N; ++i) {
v.push_back(II(h[i], i));
}
sort(v.begin(), v.end());
vector <int> ans(N);
int l = 0, r = N - 1;
for (int i = 0; i < N; ++i) {
if (i % 2) {
ans[r--] = v[i].second;
} else {
ans[l++] = v[i].second;
}
}
return ans;
}
int main(int argc, char *argv[])
{
IIVec v;
int N;
cin >> N;
for (int i = 0; i < N; ++i) {
int a;
cin >> a;
v.push_back(II(a, i));
}
sort(v.begin(), v.end());
int ans = 0;
for (int i = 0; i < N; ++i) {
ans += (i % 2) != (v[i].second % 2);
}
cout << ans / 2 << endl;
return 0;
}
vector <int> construct(vector <int> x) {
IIVec v;
for (int i = 0; i != x.size(); ++i) {
v.push_back(II(x[i], i));
}
sort(v.begin(), v.end());
vector <int> ans;
for (int i = 0; i != v.size(); ++i) {
if (v[i].first > (i + 1)) {
ans.resize(1);
ans[0] = -1;
break;
}
for (int j = 0; j < (v[i].first - 1); ++j) {
ans.push_back(v[i].second);
ans.push_back(v[j].second);
}
}
return ans;
}