好像写对了，为什么是90

#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
using namespace std;
long long c[20000],y[20000];
int main()
{
    int n;
    long long s;
    scanf("%d %lld",&n,&s);
    for(int i=1;i<=n;i++)scanf("%lld%lld",&c[i],&y[i]);
    long long sum=0;
    long long minn=2e17;
    int jl=0;
    for(long long i=1;i<=n;i++)
    {
        if(i!=1)
        minn=c[jl]*y[i]+s*y[i]*(i-jl);
        if(c[i]*y[i]<minn)jl=i,minn=c[i]*y[i];
        sum+=minn;
    }
    printf("%lld",sum);
    return 0;
}