思路：
代码：
代码语言：javascript复制#include<iostream>
#include<limits.h>
#include<cstring>
#define int long long
using namespace std;
const int N=5010;
int n,f[N],sumt[N],sumc[N],s;
//f[i][j]=f[k][j-1] (t[1] ... t[i] j*s)*(c[k 1] ... c[i])
signed main(){
cin>>n>>s;
for(int i=1;i<=n;i ){
int t,c;
cin>>t>>c;
sumt[i]=sumt[i-1] t;
sumc[i]=sumc[i-1] c;
}
memset(f,0x3f,sizeof f);
f[0]=0;
for(int i=1;i<=n;i ){
for(int j=0;j<i;j ){
f[i]=min(f[j] sumt[i]*(sumc[i]-sumc[j]) s*(sumc[n]-sumc[j]),f[i]);
}
}
cout<<f[n]<<endl;
}
