#include<bits/stdc++.h>
#define Gc() getchar()
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define eb emplace_back
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;
const int N=1e6+5,M=N*10+5,K=1000+5,mod=998244353,Mod=+-1;const db eps=1e-9;const ll INF=1e18+7;mt19937 rnd(263082);
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
int n,m,k,A[N],B[N],nxt[N],ti[N];
char s1[N],s2[N];
void make(int *A,int &len,char c1,char c2){
	scanf("%s%s",s1,s2);
	int l1=strlen(s1),l2=strlen(s2);
	len=l1*l2;
	for(int i=0;i<len;i++) A[i]=(s1[i%l1]==c1&&s2[i%l2]==c2);
}
void find(int x){
	int y=(x+n)%m;
	if(B[y]){ti[x]=1;return;}
	find(y);ti[x]=ti[y]+1;
}
void Solve(){
	int i,j;scanf("%d",&k);
	make(A,n,'T','T');make(B,m,'P','C');
	if(n>m) swap(n,m),swap(A,B);
	Me(ti,-1);
	for(i=0;i<m;i++) if(B[i]) find(i);
	priority_queue<ll> q;
	for(i=0;i<n;i++) if(A[i]&&~ti[i]) q.emplace(-(B[i]?i:i+1ll*n*ti[i]));
	while(!q.empty()){
		k--;ll p=-q.top();q.pop();
		if(!k){printf("%lld\n",p+1);return;}
		int x=p%n,y=p%m;
		q.emplace(-(p+1ll*ti[y]*n));
	}
	puts("-1");
}
int main(){
	int t=1;
	// scanf("%d",&t);
	while(t--) Solve();
	cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}