1 #include <bits/stdc++.h> 2 #define _for(i,a,b) for(int i = (a);i < b;i ++) 3 #define _rep(i,a,b) for(int i = (a);i > b;i --) 4 #define INF 0x3f3f3f3f 5 #define MOD 1000000007 6 typedef long long ll; 7 using namespace std; 8 inline ll read() 9 { 10 ll ans = 0; 11 char ch = getchar(), last = ' '; 12 while(!isdigit(ch)) last = ch, ch = getchar(); 13 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar(); 14 if(last == '-') ans = -ans; 15 return ans; 16 } 17 inline void write(ll x) 18 { 19 if(x < 0) x = -x, putchar('-'); 20 if(x >= 10) write(x / 10); 21 putchar(x % 10 + '0'); 22 } 23 struct lamp 24 { 25 int pos; 26 int power; 27 }; 28 int n,c; 29 lamp a[53]; 30 int dp[53][53][2]; 31 int sum[53][53]; 32 int main() 33 { 34 n = read(), c = read(); 35 _for(i,1,n+1) 36 a[i].pos = read(),a[i].power = read(); 37 38 _for(i,1,n+1) 39 { 40 sum[i][i] = a[i].power; 41 _for(j,i+1,n+1) 42 sum[i][j] = sum[i][j-1]+a[j].power; 43 } 44 45 memset(dp,0x3f,sizeof(dp)); 46 if(c>=2) 47 dp[c-1][c][0] = (a[c].pos-a[c-1].pos)*(sum[1][c-1]+sum[c+1][n]); 48 if(c<=n-1) 49 dp[c][c+1][1] = (a[c+1].pos-a[c].pos)*(sum[1][c-1]+sum[c+1][n]); 50 51 _for(len,3,n+1) 52 _for(l,1,n-len+2) 53 { 54 int r = l+len-1; 55 dp[l][r][0] = min(dp[l+1][r][0]+(a[l+1].pos-a[l].pos)*(sum[1][l]+sum[r+1][n]) 56 ,dp[l+1][r][1]+(a[r].pos-a[l].pos)*(sum[1][l]+sum[r+1][n])); 57 dp[l][r][1] = min(dp[l][r-1][0]+(a[r].pos-a[l].pos)*(sum[1][l-1]+sum[r][n]) 58 ,dp[l][r-1][1]+(a[r].pos-a[r-1].pos)*(sum[1][l-1]+sum[r][n])); 59 } 60 write(min(dp[1][n][0],dp[1][n][1])); 61 return 0; 62 }