#include <stdio.h>
int v[1000001];

const char *in = "operatii.in" ;
const char *out = "operatii.out" ;
int main( )
{
    freopen ( in , "r" , stdin ) ;
    freopen ( out , "w" , stdout ) ;
    int n , i , j , k ;
    k = 0 ;
    scanf ( "%d" , &n ) ;
    for ( i = 1 ; i <= n ; i++ )
    {
        scanf ( "%d" , &v[i] ) ;
    }
    for ( i = 2 ; i <= n ; i++ )
    {
        if ( v[i] > v[i-1] )
        k = k + v[i] - v[i-1] ;
    }
    printf ( "%d" , k ) ;
    return 0 ;
}