#include<cstring>
#define mo 1000000007
using namespace std;
int i,j,k,l,m,n;
int x,y;
int t=0;
long long a[1002][1002];
int gcd(int x,int y){
if (y==0) return x;
else gcd(y,x%y);
}
int main(){
freopen("test.in","r",stdin);
freopen("test.out","w",stdout);
scanf("%d%d%d",&n,&m,&k);
memset(a,0,sizeof(a));
a[1][1]=1;
for (i=1;i<=n+1;i++)
for (j=1;j<=m+1;j++){
if (i==1 && j==1) a[i][j]=1;
else a[i][j]=(a[i-1][j]+a[i][j-1])%mo;
}
long long sum=a[n+1][m+1];
for (x=n+1;x>=1;x--)
for (y=m+1;y>=1;y--){
if (x+1<=n+1){
i=x+1;
j=y;
long long sum2=((sum-a[x][y]*a[n+2-i][m+2-j]%mo)+mo)%mo;
if (sum2==k) t++;
}
if (y+1<=m+1){
i=x;
j=y+1;
long long sum2=((sum-a[x][y]*a[n+2-i][m+2-j]%mo)+mo)%mo;
if (sum2==k) t++;
}
}
int s=m*(n+1)+n*(m+1);
if (t==s) printf("1");
else {
int gys=gcd(s,t);
printf("%d/%d",t/gys,s/gys);
}
}