1 #include<stdio.h>
 2 #include<string.h>
 3 const int MAXN=5010;
 4 const int INF=0xfffffff;
 5 #define MAX(x,y) (x>y?x:y)
 6 int dp[MAXN][2];
 7 char a[MAXN],b[MAXN];
 8 int main(){
 9     int t,i,j;
10     while(~scanf("%d",&t)){
11         scanf("%s",a+1);
12         //printf("%d\n",t);
13         for(i=t,j=1;i>0;i--,j++)b[j]=a[i];
14         b[j]=‘\0‘;
15         //printf("%s\n",b+1);
16         memset(dp,0,sizeof(dp));
17         dp[0][0]=0;
18         for(i=1;i<=t;i++){
19             for(j=1;j<=t;j++){
20                 if(a[i]==b[j])dp[j][i%2]=dp[j-1][(i-1)%2]+1;
21                 else dp[j][i%2]=MAX(dp[j-1][i%2],dp[j][(i-1)%2]);
22             }
23         }
24         //printf("%d\n",dp[t][t%2]);
25         printf("%d\n",t-dp[t][t%2]);
26     }
27 return 0;}