#include using namespace std; #define rep(i,n) for(ll i=0;i=0;i--) #define perl(i,r,l) for(ll i=r-1;i>=l;i--) #define fi first #define se second #define ins insert #define pqueue(x) priority_queue,greater> #define all(x) (x).begin(),(x).end() #define CST(x) cout<; using vvl=vector>; using pl=pair; using vpl=vector; using vvpl=vector; const ll MOD=1000000007; const ll MOD9=998244353; const int inf=1e9+10; const ll INF=4e18; const ll dy[9]={1,0,-1,0,1,1,-1,-1,0}; const ll dx[9]={0,1,0,-1,1,-1,1,-1,0}; template inline bool chmax(T &a, T b) { return ((a < b) ? (a = b, true) : (false)); } template inline bool chmin(T &a, T b) { return ((a > b) ? (a = b, true) : (false)); } int main(){ ll n,m;cin >> n >> m; if(n*m>1e7){ vl mle(INF); } vl dp(m+1,-INF);dp[m]=0; rep(i,n){ ll a,b;cin >> a >> b; repl(j,1,m+1){ dp[j]+=max({a*(j-1)+b,a*j,b}); } per(j,m)chmax(dp[j],dp[j+1]); //rep(j,m+1)cout << dp[j] <<" ";cout << endl; } cout << dp[0] << endl; }