Maybe I need to use bignum but I am not sure if it is really necesary to use bignum or not...maybe my code has another error

here is my code:

#include <stdio.h>
long long cmb[100][100],res;

c(n,k){
    int i,j;
    for(i=0;i<=n;i++){
      cmb[i][0]=1;
      cmb[i][i]=1;
    }
    for(i=1;i<=n;i++)
        for(j=1;j<=k;j++)
          cmb[i][j]=cmb[i-1][j-1] + cmb[i-1][j];
     return cmb[n][k];
}

int main(){
  int n,a,b;
  scanf("%d %d %d",&n,&a,&b);
  res=c(n+a,a)*c(n+b,b);
  printf("%I64d\n",res);
  return 0;
}


thanks for reading
bye