codeforces252-B - Valera and Fruits

#include<iostream>#include<cstdio>#include<cmath>#include<algorithm>#include<memory.h>#include<map>#include<queue>#include <deque>#include <list>#include <ctime>#include <stack>#include <vector>#include<set>#define Maxn 3005typedef long long ll;#define rep(i,j,n) for(int i=j;i<=n;i++)#define per(i,j,k) for(int i=j;i>=k;--i)#define lowbit(a) a&-a#define Max(a,b) a>b?a:b#define Min(a,b) a>b?b:aconst int inf = 0x3f3f3f3f;const double pi = acos(-1.0);using namespace std;int a,b,t[Maxn];int main(){   int n,v,sum=0,tmp=0;    int end_t=-1,start_t=9999;    scanf("%d%d",&n,&v);    rep(i,1,n)    {scanf("%d%d",&a,&b);     t[a]+=b;     end_t=Max(end_t,a);     start_t=Min(start_t,a);    }    rep(i,start_t,end_t+1)    {        if(tmp>=v)tmp=t[i],sum+=v;        else        {   if(tmp+t[i]<=v)sum+=tmp+t[i],tmp=0;            else tmp=t[i]-(v-tmp),sum+=v;        }    }    printf("%d\n",sum);    return 0;}