#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, U b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, U b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
template <class T, class T1>
inline void print(T first, T1 second) {
  printsp(first), println(second);
}
template <class T, class T1, class T2>
inline void print(T first, T1 second, T2 z) {
  printsp(first), printsp(second), println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
struct segment {
  int L, R;
  double p;
  segment(int L = 0, int R = 0, double p = 0) : L(L), R(R), p(p) {}
  bool operator<(const segment &s) const {
    if (L == s.L) return R > s.R;
    return L < s.L;
  }
} seg[5050];
int a[100100];
int mx[100100][20];
void pre(int n) {
  for (int i = 1; i <= n; i++) mx[i][0] = a[i];
  for (int j = 1; j < 20; j++)
    for (int i = 1; i <= n; i++) {
      mx[i][j] = max(mx[i][j - 1], mx[min(n, i + (1 << j - 1))][j - 1]);
    }
}
int calc(int L, int R) {
  int l = 31 - (__builtin_clz(R - L + 1));
  return max(mx[L][l], mx[R - (1 << l) + 1][l]);
}
vector<int> adj[5050];
int val[5050];
int cur, m;
void build(int u) {
  val[u] = calc(seg[u].L, seg[u].R);
  while (cur < m) {
    if (seg[cur].L > seg[u].R) return;
    int v = cur++;
    adj[u].push_back(v);
    build(v);
  }
}
double dp[5050][5050];
void solve(int u) {
  for (int j = 0; j < 5050; j++) dp[u][j] = 1;
  for (int i = 0; i < adj[u].size(); i++) {
    int v = adj[u][i];
    solve(v);
    for (int j = 0; j < 5050; j++) {
      int k = min(5050 - 1, val[u] + j - val[v]);
      dp[u][j] *= dp[v][k];
    }
  }
  for (int j = 5050; j--;) {
    dp[u][j] = dp[u][j] * (1 - seg[u].p);
    if (j) dp[u][j] += dp[u][j - 1] * seg[u].p;
  }
}
int main() {
  int n, m;
  gn(n, m);
  for (int i = 1; i <= n; i++) gn(a[i]);
  pre(n);
  for (int i = 0; i < m; i++) {
    gn(seg[i].L, seg[i].R);
    scanf("%lf", &seg[i].p);
  }
  seg[m++] = segment(1, n, 0);
  sort(seg, seg + m);
  cur = 1;
  ::m = m;
  build(0);
  solve(0);
  double ans = 0;
  for (int j = 5050; j--;) {
    if (j) dp[0][j] -= dp[0][j - 1];
    ans += dp[0][j] * (val[0] + j);
  }
  printf("%.9lf\n", ans);
  return 0;
}
