#include using namespace std;
//思路：将输入的所有区域坐标点插上1，即使重合区域也不影响； //最后遍历0-L，坐标点为1的就是要移走的，最后别忘了+1 int main() { int temp = 0; int sum = 0; int L, M; cin >> L >> M; int flag[10000] = { 0 }; for (int i = 0; i < M; i++) { int a = 0; int b = 0; cin >> a >> b; for (int j = a; j <= b; j++) { flag[j] = 1; } } for (int i = 0; i <= L; i++) { if (flag[i] == 1) { ++temp; } } sum = L - temp + 1; cout << sum; return 0; }