diff --git a/100.c b/100.c
new file mode 100644
index 0000000..b7124b1
--- /dev/null
+++ b/100.c
@@ -0,0 +1,127 @@
+/* UVa Online Judge
+ * 100 - The 3n+1 Problem
+ * Author: Grace Chin */
+
+#include <stdio.h>
+
+#define DEBUG 0
+
+unsigned int get_cycle_length( unsigned int n ) ;
+
+int main( int argc, char* argv[] ) {
+
+  unsigned int i ; /* 0 < i < 10,000 */
+  unsigned int j ; /* 0 < i < 10,000 */
+  unsigned int n ;
+  unsigned int cycle_length ;
+  unsigned int maximum_cycle_length = 0 ;
+
+  /* Get input */
+  printf( "Please enter an i and a j: " ) ;
+
+  while ( scanf( "%u %u", &i, &j ) ) {
+
+    if ( DEBUG == 1 ) {
+      printf( "\n" ) ;
+    }
+    
+    /* For i to j, including i and j... */
+    for ( n = i ; n < ( j + 1 ) ; n++ ) { 
+
+      /* Get cycle length */
+      cycle_length = get_cycle_length( n ) ;
+
+      if ( DEBUG == 1 ) {
+	printf( "n is %u.\n", n ) ;
+	printf( "The cycle length is %u.\n", cycle_length ) ;
+      }
+
+      /* Update maximum cycle length */
+      if ( cycle_length > maximum_cycle_length ) {
+
+	maximum_cycle_length = cycle_length ;
+
+	if ( DEBUG == 1 ) {
+	  printf( "The maxiumum cycle length has been updated to %u.\n", cycle_length ) ;	  
+	}
+
+      }
+
+      if ( DEBUG == 1 ) {
+	printf( "\n" ) ;
+      }
+      
+    }
+  
+    /* Print output */
+    printf( "%u %u %u\n", i, j, maximum_cycle_length ) ;
+
+    /* Reset maximum cycle length */
+    maximum_cycle_length = 0 ;
+
+  }
+  
+  return 0 ;
+
+}
+
+unsigned int get_cycle_length( unsigned int n ) {
+
+  unsigned int cycle_length = 1 ;
+
+  if ( DEBUG == 2 ) {
+    printf( "\n" ) ;
+  }
+  
+  /* Repeat as long as n is not 1... */
+  while ( n != 1 ) {
+
+    if ( DEBUG == 2 ) {
+      printf( "n is %u.\n", n ) ;
+    }
+    
+    /* If n is odd... */
+    if ( n % 2 == 1 ) {
+
+      /* Multiply n by 3 and add 1. */
+      n = ( 3 * n ) + 1 ;
+
+      if ( DEBUG == 2 ) {
+	printf( "n is odd, so n has been updated to 3n+1, which is %u.\n", n ) ;
+      }
+
+      /* Update cycle length. */
+      cycle_length += 1 ;
+	
+      if ( DEBUG == 2 ) {
+	printf( "The cycle length has been updated to %d.\n", cycle_length ) ;
+      }
+
+      /* If n is even... */
+    } else {
+
+      /* Divide n by 2. */
+      n = n / 2 ;
+	  
+      if ( DEBUG == 2 ) {
+	printf( "n is not odd, so n has been updated to n/2, which is %u.\n", n ) ;	  
+      }
+
+      /* Update cycle length. */
+      cycle_length += 1 ;
+
+      if ( DEBUG == 2 ) {
+	printf( "The cycle length has been updated to %u.\n", cycle_length ) ;
+      }
+	
+    }
+
+    if ( DEBUG == 2 ) {
+      printf( "\n" ) ;
+    }
+    
+  }
+
+  return cycle_length ;
+
+}