441B - Valera and Fruits - CodeForces Solution

#include<bits/stdc++.h>

using namespace std;

int main(){


int t=1;
//cin>>t;
int s=t;

while(t--){
int n,v;
cin>>n>>v;

int ar[10000]={0};
int a,b;
int maxi=INT_MIN;
for(int i=0;i<n;i++){

        cin>>a>>b;
        maxi=max(a,maxi);

        ar[a]=ar[a]+b;

}

int f=0;

for(int i=1;i<maxi+2;i++){
if(ar[i]<=v){
  f=f+ar[i];
}
else if(ar[i]>v&&ar[i]<=v*2){
        f=f+v;
        ar[i+1]=ar[i+1]+(ar[i]-v);

}
else{
    f=f+v;
    ar[i+1]=ar[i+1]+v;
}
}


cout<<f<<endl;




}



return 0;
}