#include <iostream> #include <vector> #include <algorithm> #include <string> #include <map> #include <stack> using namespace std; int n, d; int x, y; int field[20][20]; int main() { cin >> n >> d; int dp[101][2]={0};//0が東京,1が京都 vector<pair<int, int>> fee(101); for(int i=0; i<n; ++i){ int a, b; cin >> a >> b; fee[i].first = a; fee[i].second = b; } dp[1][0] = fee[0].first; dp[1][1] = fee[0].second-d; for(int i=1; i<n; ++i){ dp[i+1][0] = fee[i].first + max(dp[i][0], dp[i][1]-d); dp[i+1][1] = fee[i].second + max(dp[i][0]-d, dp[i][1]); } cout <<max(dp[n][0], dp[n][1]) << endl; return 0; }