100pts 马风良好 subtask#1后两个测试点WA

123456789101112131415161718192021222324252627282930313233343536373839404142#include<bits/stdc++.h>
using namespace std;
int n,k,max_d,ans,a[300005];
inline int read() {
	int n=0,f=1;
	char ch=getchar();
	while(!isdigit(ch)) {
		if(ch=='-') f=-1;
		ch=getchar();
	}
	while(isdigit(ch)) {
		n=n*10+ch-'0';
		ch=getchar();
	}
	return f*n;
}
inline void write(int n) {
	if(n<0) putchar('-'),n=-n;
	if(n<10) putchar(n+'0');
	else write(n/10),putchar(n%10+'0'); 
}
int main() {
	n=read(),k=read();
	for(int i=1;i<=n;i++) {
		int d=read(),m=read();
		a[d]+=m;
		max_d=max(max_d,d);
	}
	for(int i=1;i<=max_d+1;i++) {
        int save=k;
		if(a[i-1]>0) {
            if(a[i-1]>=save) ans+=save,save=0;
            else save-=a[i-1],ans+=a[i-1];
        }
        if(save>0&&a[i]>0) {
            if(a[i]>=save) ans+=save,a[i]-=save;
            else ans+=a[i],a[i]=0;
        }
	}
	write(ans);
	return 0;
}