// #pragma GCC target("avx")  // CPU 処理並列化
// #pragma GCC optimize("O3")  // CPU 処理並列化
// #pragma GCC optimize("unroll-loops")  // 条件処理の呼び出しを減らす
// #define BEGIN_STACK_EXTEND(size) void * stack_extend_memory_ = malloc(size);void * stack_extend_origin_memory_;char * stack_extend_dummy_memory_ = (char*)alloca((1+(int)(((long long)stack_extend_memory_)&127))*16);*stack_extend_dummy_memory_ = 0;asm volatile("mov %%rsp, %%rbx\nmov %%rax, %%rsp":"=b"(stack_extend_origin_memory_):"a"((char*)stack_extend_memory_+(size)-1024));
// #define END_STACK_EXTEND asm volatile("mov %%rax, %%rsp"::"a"(stack_extend_origin_memory_));free(stack_extend_memory_);

#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<deque>
#include<stack>
#include<string>
#include<string.h>
#include<vector>
#include<set>
#include<map>
#include<bitset>
#include<stdlib.h>
#include<cassert>
#include<time.h>
#include<bitset>
#include<numeric>
#include<unordered_set>
#include<unordered_map>
#include<complex>
using namespace std;
const long long mod=998244353;
const long long inf=mod*mod;
const long long d2=(mod+1)/2;
const double EPS=1e-11;
const double INF=1e+10;
const double PI=acos(-1.0);
const int C_SIZE = 11100000;
const int UF_SIZE = 3100000;
namespace{
	long long fact[C_SIZE];
	long long finv[C_SIZE];
	long long inv[C_SIZE];
	inline long long Comb(int a,int b){
	 	if(a<b||b<0)return 0;
	 	return fact[a]*finv[b]%mod*finv[a-b]%mod;
	}
	void init_C(int n){
		fact[0]=finv[0]=inv[1]=1;
		for(int i=2;i<n;i++){
			inv[i]=(mod-(mod/i)*inv[mod%i]%mod)%mod;
		}
		for(int i=1;i<n;i++){
			fact[i]=fact[i-1]*i%mod;
			finv[i]=finv[i-1]*inv[i]%mod;
		}
	}
	long long pw(long long a,long long b){
		if(a<0LL)return 0;
		if(b<0LL)return 0;
		long long ret=1;
		while(b){
			if(b%2)ret=ret*a%mod;
			a=a*a%mod;
			b/=2;
		}
		return ret;
	}
	long long pw_mod(long long a,long long b,long long M){
		if(a<0LL)return 0;
		if(b<0LL)return 0;
		long long ret=1;
		while(b){
			if(b%2)ret=ret*a%M;
			a=a*a%M;
			b/=2;
		}
		return ret;
	}
	int pw_mod_int(int a,int b,int M){
		if(a<0)return 0;
		if(b<0)return 0;
		int ret=1;
		while(b){
			if(b%2)ret=(long long)ret*a%M;
			a=(long long)a*a%M;
			b/=2;
		}
		return ret;
	}
	int ABS(int a){return max(a,-a);}
	long long ABS(long long a){return max(a,-a);}
	double ABS(double a){return max(a,-a);}
	int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }
	int UF[UF_SIZE];
	void init_UF(int n){
		for(int i=0;i<n;i++)UF[i]=-1;
	}
	int FIND(int a){
		if(UF[a]<0)return a;
		return UF[a]=FIND(UF[a]);
	}
	void UNION(int a,int b){
		a=FIND(a);b=FIND(b);if(a==b)return;
		if(UF[a]>UF[b])swap(a,b);
		UF[a]+=UF[b];UF[b]=a;
	}
}
// ここから編集しろ
string t[1100000];
char in[1100000];
vector<pair<int,int> > g[1100000];
long long ijk[1100000][4];
int v[1100000][4];
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
int main(){
	int a,b,c;scanf("%d%d%d",&a,&b,&c);
	int X1,X2,Y1,Y2;
	scanf("%d%d%d%d",&X1,&Y1,&X2,&Y2);
	X1--;Y1--;X2--;Y2--;
	for(int i=0;i<a;i++){
		scanf("%s",in);
		t[i]=in;
	}
	priority_queue<pair<long long,pair<int,int> > >Q;
	for(int i=0;i<a*b;i++){
		for(int j=0;j<4;j++)ijk[i][j]=inf;
	}
	ijk[X1*b+Y1][0]=0;
	Q.push(make_pair(0LL,make_pair(X1*b+Y1,0)));
	while(Q.size()){
		long long cost=-Q.top().first;
		int at=Q.top().second.first;
		int dir=Q.top().second.second;Q.pop();
		if(v[at][dir])continue;
		v[at][dir]=1;
		int row=at/b;
		int col=at%b;
		int tr=row+dx[dir];
		int tc=col+dy[dir];
		if(0<=tr&&tr<a&&0<=tc&&tc<b&&t[tr][tc]!='@'){
			if(ijk[tr*b+tc][dir]>cost+1){
				ijk[tr*b+tc][dir]=cost+1;
				Q.push(make_pair(-cost-1,make_pair(tr*b+tc,dir)));
			}
		}
		long long toc=cost+(c-cost%c)%c;
		if(ijk[row*b+col][(dir+1)%4]>toc){
			ijk[row*b+col][(dir+1)%4]=toc;
			Q.push(make_pair(-toc,make_pair(row*b+col,(dir+1)%4)));
		}
	}
	long long ret=inf;
	for(int i=0;i<4;i++){
		ret=min(ret,ijk[X2*b+Y2][i]+(c-ijk[X2*b+Y2][i]%c)%c);
	}
	if(ret==inf)ret=-c;
	printf("%lld\n",ret/c);
}

Measured memory_bytes: 113356