#include<stdlib.h>
#include<math.h>
#include<string.h>
#define jz 1000000007
int n,m,kk,cgb;
long long map[1010][1010];
int gcd(int a,int b)
{
if(a%b)
return (gcd(b,a%b));
return (b);
}
void init(void)
{
int i,k;
scanf("%d%d%d",&n,&m,&kk);
cgb=n*(m+1)+m*(n+1);
n++; m++;
for(i=1;i<=n;i++)
map[i][1]=1;
for(i=1;i<=m;i++)
map[1][i]=1;
for(i=2;i<=n;i++)
{
for(k=2;k<=m;k++)
map[i][k]=(map[i-1][k]+map[i][k-1])%jz;
}
return;
}
void run(void)
{
int i,k,j,ans=0;
long long jj;
for(i=1;i<=n;i++)
{
for(k=1;k<=m;k++)
{
jj=(map[i][k-1]*map[n-i+1][m-k+1])%jz;
if(((map[n][m]+jz)-jj)%jz==kk)
ans++;
jj=(map[i-1][k]*map[n-i+1][m-k+1])%jz;
if(((map[n][m]+jz)-jj)%jz==kk)
ans++;
}
}
if(ans==0||cgb==ans)
{
printf("%d\n",ans/cgb);
return;
}
j=gcd(cgb,ans);
printf("%d/%d\n",ans/j,cgb/j);
return;
}
int main(void)
{
init();
run();
return (0);
}