Common Subsequence

 #include<cstdio>
 #include<iostream>
 #include<cmath>
 #include<string>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 int a[][];
 int main()
 {
     string s1,s2;
     while(cin>>s1>>s2)
     {
         int k1=s1.length();
         int k2=s2.length();
         memset(a,,sizeof(a));
         for(int i=; i<=k1; i++)
         {
             for(int j=; j<=k2; j++)
             {
                 if(s1[i-]==s2[j-])
                 {
                     a[i%][j]=a[(i-)%][j-]+;
                 }
                 else
                 {
                     a[i%][j]=max(a[(i-)%][j],a[i%][j-]);
                 }
             }
         }
         printf("%d\n",a[k1%][k2]);
     }
     return ;
 }