#include <bits/stdc++.h>   using namespace std;   const int M = 105;   int l[M], r[M], t[M], c[M], res[M], p[M];   int main() {     int n, m;     cin >> n >> m;     for (int i = 0; i < m; ++i) {       cin >> l[i] >> r[i] >> t[i] >> c[i];     }     for (int i = 1; i <= n; ++i) p[i] = INT_MAX;     for (int i = 0; i < m; ++i)       for (int j = l[i]; j <= r[i]; ++j)         if (t[i] < p[j]) p[j] = t[i], res[j] = i;     int sum = 0;     for (int i = 1; i <= n; ++i)       if (p[i] != INT_MAX) sum += c[res[i]];     cout << sum << endl;   }   