namrita_adobe.cpp

#include <bits/stdc++.h>
using namespace std ; 
#define REP(i, a, b) for (int i = a; i <= b; i++)
#define FOR(i, n) for (int i = 0; i < n; i++)
#define foreach(it, ar) for ( typeof(ar.begin()) it = ar.begin(); it != ar.end(); it++ )
#define fill(ar, val) memset(ar, val, sizeof(ar))
#define PI 3.1415926535897932385
#define uint64 unsigned long long
#define Int long long
#define int64 long long
#define all(ar) ar.begin(), ar.end()
#define pb push_back
#define ff first
#define ss second
#define bit(n) (1<<(n))
#define Last(i) ( (i) & (-i) )
#define sq(x) ((x) * (x))
#define mp make_pair
const int MAXN = 351 ; 
int dp[ MAXN ][ MAXN ][ MAXN ]  ;
char A[ MAXN ] ; 
char B[ MAXN ] ; 
int N , M , K ; 
const int INF = 1e8 ; 

int comp ( char a ,  char b )
 {
 	 return ( a - 'a' )^( b - 'a' ) ; 
 }

int rec(  int i , int j , int LCS )
 {
  
    if( LCS >= K ) 
           return 0 ;   
    if( i == N or j == M )
         return INF ;                	
   
    int cost = INF ; 

    if( dp[i][j][LCS] != -1 )return dp[i][j][LCS] ; 

    if( A[i] == B[j] )
       cost = min(cost,rec( i + 1 , j + 1 , LCS + 1 )) ; 
    cost = min( cost , comp(A[i],B[j] ) + rec( i + 1 , j + 1 , LCS +  1 ) )  ;     
    cost = min( cost , rec(i,j+1,LCS) ) ; 
    cost = min( cost , rec(i+1,j,LCS) ) ; 
    dp[i][j][LCS] = cost ; 
    return cost  ; 
 }

int main() 
 { 
    memset( dp, -1 , sizeof(dp) ) ; 
    scanf("%d%d%d",&N,&M,&K) ; 
    scanf(" %s",A) ; 
    scanf(" %s",B) ; 

    int ans = rec( 0 , 0 , 0 ) ;
    if( ans >= INF )ans = -1 ; 
    printf("%d\n",ans );   

 }