#include <cstdio>

 #include <cstdlib>

 #include <cstring>

 #define MAXN 25

 int dp[MAXN][MAXN*];

 void init() {

     int i, j, k;

     memset(dp, , sizeof(dp));

     dp[][] = dp[][] = dp[][] = dp[][] = ;

     for (i=; i<MAXN; ++i) {

         for (j=; j<MAXN*; ++j) {

             dp[i][j] += dp[i-][j-];

             if (j >= )

                 dp[i][j] += dp[i-][j-];

             if (j >= )

                 dp[i][j] += dp[i-][j-];

         }

     }

 }

 int main() {

     int a, b, t;

     int i, j, k, tmp;

     int mmin, mmax;

     __int64 ans;

     #ifndef ONLINE_JUDGE

         freopen("data.in", "r", stdin);

     #endif

     init();

     while (scanf("%d %d %d", &a, &b, &t) != EOF) {

         i = t / ;

         j = (i+) / ;

         if (b < a) {

             tmp = a - b;

             mmin = j;

             mmax = j * ;

         } else {

             tmp = b - a;

             mmin = tmp + i - j + ;

             mmax = j * ;

         }

         ans = ;

         for (k=mmin; k<=mmax; ++k)

             ans += dp[j][k];

         printf("%I64d\n", ans);

     }

     return ;

 }