P12244 踩点

#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 100;
#define maxn 10010
#define mod 1e9 + 7
#define upto(i, a, b) for (int i = a; i <= b; i++)
#define downto(i, a, b) for (int i = a; i >= b; i--)
#define rep(i, a, b) for (int i = a; i < b; i++)
int main()
{
    int n, t, end = 0;
    int tot = 0;//打球的总时间
    cin >> n >> t;
    int start[N], end[N];
    upto(i, 1, n)
    {
        cin >> start[i] >> end[i];
    }
    upto(i, 1, n)
    {
        if (i > 1)//不用看start[1]
        {
            int jian = start[i] - end[i - 1];
            if (jian > t)//只要不迟到
            {
                tot += (jian - t);
            }
        }
    }
    cout << tot;
    return 0;
}